Direct SQL Read Question
HI Experts,
Do we have a transaction for Direct SQL Access?
I have to execute oracle commands:
SELECT * FROM DBA_ROLE_PRIVS
SELECT * FROM DBA_USERS
SELECT * FROM DBA_SYS_PRIVS
WHERE
PRIVILEGE='CREATE USER' OR
PRIVILEGE='BECOME USER' OR
PRIVILEGE='ALTER USER' OR
PRIVILEGE='DROP USER' OR
PRIVILEGE='CREATE ROLE' OR
PRIVILEGE='ALTER ANY ROLE' OR
PRIVILEGE='DROP ANY ROLE' OR
PRIVILEGE='GRANT ANY ROLE' OR
PRIVILEGE='CREATE PROFILE' OR
PRIVILEGE='ALTER PROFILE' OR
PRIVILEGE='DROP PROFILE' OR
PRIVILEGE='CREATE ANY TABLE' OR
PRIVILEGE='ALTER ANY TABLE' OR
PRIVILEGE='DROP ANY TABLE' OR
PRIVILEGE='INSERT ANY TABLE' OR
PRIVILEGE='UPDATE ANY TABLE' OR
PRIVILEGE='DELETE ANY TABLE' OR
PRIVILEGE='CREATE ANY PROCEDURE' OR
PRIVILEGE='ALTER ANY PROCEDURE' OR
PRIVILEGE='DROP ANY PROCEDURE' OR
PRIVILEGE='CREATE ANY TRIGGER' OR
PRIVILEGE='ALTER ANY TRIGGER' OR
PRIVILEGE='DROP ANY TRIGGER' OR
PRIVILEGE='CREATE TABLESPACE' OR
PRIVILEGE='ALTER TABLESPACE' OR
PRIVILEGE='DROP TABLESPACES' OR
PRIVILEGE='ALTER DATABASE' OR
PRIVILEGE='ALTER SYSTEM'
Any suggestions?
Moderator Message: You have already asked this question in another thread. Thread locked.
Hi,
Thanks for your reply. So I still have to create a program for Native SQL Statements?
Or do you have other ideas on how to do this without creating programs? Please consider the tables that I want to read (please refer to my previous post) are not seen in SE16n or SQVI (not in ABAP Doctionary).
Thanks a Lot!
Similar Messages
-
Hi Experts,
Do you have any ideas on how to access the database tables below? It is not in the SAP ABAP Dictionary.
SELECT * FROM DBA_ROLE_PRIVS
SELECT * FROM DBA_USERS
SELECT * FROM DBA_SYS_PRIVS
WHERE
PRIVILEGE='CREATE USER' OR
PRIVILEGE='BECOME USER' OR
PRIVILEGE='ALTER USER' OR
PRIVILEGE='DROP USER' OR
PRIVILEGE='CREATE ROLE' OR
PRIVILEGE='ALTER ANY ROLE' OR
PRIVILEGE='DROP ANY ROLE' OR
PRIVILEGE='GRANT ANY ROLE' OR
PRIVILEGE='CREATE PROFILE' OR
PRIVILEGE='ALTER PROFILE' OR
PRIVILEGE='DROP PROFILE' OR
PRIVILEGE='CREATE ANY TABLE' OR
PRIVILEGE='ALTER ANY TABLE' OR
PRIVILEGE='DROP ANY TABLE' OR
PRIVILEGE='INSERT ANY TABLE' OR
PRIVILEGE='UPDATE ANY TABLE' OR
PRIVILEGE='DELETE ANY TABLE' OR
PRIVILEGE='CREATE ANY PROCEDURE' OR
PRIVILEGE='ALTER ANY PROCEDURE' OR
PRIVILEGE='DROP ANY PROCEDURE' OR
PRIVILEGE='CREATE ANY TRIGGER' OR
PRIVILEGE='ALTER ANY TRIGGER' OR
PRIVILEGE='DROP ANY TRIGGER' OR
PRIVILEGE='CREATE TABLESPACE' OR
PRIVILEGE='ALTER TABLESPACE' OR
PRIVILEGE='DROP TABLESPACES' OR
PRIVILEGE='ALTER DATABASE' OR
PRIVILEGE='ALTER SYSTEM'
Thanks a lot!Looks like you need ABAP DB Connectivity classes for this purpose. (e.g., CL_SQL* classes)
Check the demo program ADBC_DEMO.
BR,
Suhas -
Direct Path Read waits are not showing in Elapsed time
Hi,
I'm having a question regarding interpretation of a SQL trace file. I'm on Oracle 11.2.0.1 HP/UX 64 bit.
Following is only the overall result of the trace (it is quite big).
My question is about the Direct Path Read waits which are totallizing 268s of wait but are not showing in the fetch elapsed time (49.58s) and are not showing anywhere in the trace except in the overall result.
I do not understand why it is not part of the Elapsed time...
For info, the trace is for the specific session that was performing all the required queries to display an online report. The database is accessed by the Java application using Hybernate.
The trace was obtained by the following SQL:
exec sys.dbms_monitor.serv_mod_act_trace_enable(service_name=>'SYS$USERS',waits=>true,binds=>true);Then I query the sessions to find the one created by the application.
OVERALL TOTALS FOR ALL NON-RECURSIVE STATEMENTS
call count cpu elapsed disk query current rows
Parse 36 0.43 0.51 0 5 0 0
Execute 62 0.01 0.01 0 0 0 0
Fetch 579 4.01 49.06 3027 153553 0 5516
total 677 4.45 49.58 3027 153558 0 5516
Misses in library cache during parse: 29
Misses in library cache during execute: 2
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
SQL*Net message to client 32754 0.00 0.03
SQL*Net message from client 32753 2.33 232.01
Disk file operations I/O 179 0.00 0.02
db file sequential read 2979 0.54 45.72
SQL*Net more data to client 133563 0.04 5.30
direct path read 34840 0.94 268.21
SQL*Net more data from client 1075 0.00 0.02
db file scattered read 6 0.03 0.11
asynch descriptor resize 52 0.00 0.00
OVERALL TOTALS FOR ALL RECURSIVE STATEMENTS
call count cpu elapsed disk query current rows
Parse 25 0.00 0.02 0 0 0 0
Execute 58 0.05 0.04 0 0 0 0
Fetch 126 0.00 0.04 4 161 0 123
total 209 0.05 0.11 4 161 0 123
Misses in library cache during parse: 3
Misses in library cache during execute: 3
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
Disk file operations I/O 1 0.00 0.00
db file sequential read 4 0.01 0.03
asynch descriptor resize 1 0.00 0.00
37 user SQL statements in session.
57 internal SQL statements in session.
94 SQL statements in session.
Trace file: oxd1ta00_ora_16542.trc
Trace file compatibility: 11.1.0.7
Sort options: default
1 session in tracefile.
37 user SQL statements in trace file.
57 internal SQL statements in trace file.
94 SQL statements in trace file.
57 unique SQL statements in trace file.
241517 lines in trace file.
568 elapsed seconds in trace file.Thanks
ChristopheChristophe Lize wrote:
Closing this thread even if it's not answered...Sorry, I don't have time to test this myself now, but you shouldn't mark this thread as answered if it is not, because other people might find it and think they find an answer if they have a similar question.
I suggest you try the following to narrow down things:
1. Open the RAW trace file and check the cursor numbers of the "direct path reads" - check if you can find any references for those cursor numbers manually. The cursor numbers are those numbers behind the WAIT #<xx>, and you can check if you find any other entry unequal to WAIT #<xx> with the same #<xx>, for example EXEC #<xx> or FETCH #<xx>
A short primer on how to interpret the raw trace file can also be found in MOS document 39817.1
2. Run the RAW trace file through alternative free trace file analyzers like SQLDeveloper (yes it can process raw trace files), OraSRP or Christian Antognini's TVD$XTAT. If you have My Oracle Support access you can also try Oracle's own extended Trace Analyzer (TRCA / TRCANLZR). See MOS Note 224270.1
Check if these tools tell you more about your specific wait event and oddities with the trace file in general.
Regards,
Randolf
Oracle related stuff blog:
http://oracle-randolf.blogspot.com/
Co-author of the "OakTable Expert Oracle Practices" book:
http://www.apress.com/book/view/1430226684
http://www.amazon.com/Expert-Oracle-Practices-Database-Administration/dp/1430226684 -
Query Tuning (sequential read + direct path read/write temp)
Following query takes nearly 10 minutes under 10.2.0.2 on WIN2K3 to execute but I am sure there would be an alternate to tune it further.
Major waits are 'db file sequential read' and 'direct path read temp' in addition to 'direct path write temp'
Increasing/tuning the work_area_policy/sort_area_size would help? moving the tables to faster disk would reduce PIO causing sequential read, query re-writing would prove to be helpful?.
Below is the tkprof:
SELECT
P.PER_ID
, CL.DESCR
, P.ENG_NAME
, P.ARA_NAME
, P.NATION
, P.ADDR
, ('Mob:' || NVL(P.MOB, '') || ', Home:' || NVL(P.HOME, '') || ', Bus.:' || NVL(P.BUS, '') || ', Fax:' || NVL(P.FAX, '')) PHONE
, SUM(CASE
WHEN FT.FT_TYPE_FLG IN ('BS','BX','AD','AX') THEN FT.CUR_AMT
ELSE 0
END) BILL
, SUM(CASE
WHEN FT.FT_TYPE_FLG IN ('PS','PX') THEN FT.CUR_AMT * -1
ELSE 0
END) PAY
, SUM(FT.CUR_AMT) DUE
, SUM(CASE
WHEN FT.FREEZE_DTTM > '03-JUN-08' THEN
CASE WHEN FT.FT_TYPE_FLG IN ('PS','PX') THEN FT.CUR_AMT * -1
ELSE 0
END
ELSE 0
END) PAY_02JUN
FROM
CI_FT FT
, CI_SA SA
, CI_ACCT_CHAR AC
, CI_CUST_CL_L CL
, CI_ACCT A
, CI_ACCT_PER AP
SELECT
P.PER_ID
, (P.CITY || ', ' || P.STATE || ',' || P.COUNTRY) ADDR
, MAX(DECODE(PP.PHONE_TYPE_CD, 'MOB ', PP.PHONE)) MOB
, MAX(DECODE(PP.PHONE_TYPE_CD, 'BUSN ', PP.PHONE)) BUS
, MAX(DECODE(PP.PHONE_TYPE_CD, 'HOME ', PP.PHONE)) HOME
, MAX(DECODE(PP.PHONE_TYPE_CD, 'FAX ', PP.PHONE)) FAX
, MAX(DECODE(PN.NAME_TYPE_FLG, 'PRIM', PN.ENTITY_NAME)) ENG_NAME
, MAX(DECODE(PN.NAME_TYPE_FLG, 'ALT ', PN.ENTITY_NAME)) ARA_NAME
, MAX(DECODE(PC.CHAR_TYPE_CD, 'NATION ', PC.CHAR_VAL)) NATION
FROM
CI_PER P
, CI_PER_PHONE PP
, CI_PER_NAME PN
, CI_PER_CHAR PC
WHERE
P.PER_ID = PP.PER_ID (+)
AND P.PER_ID = PN.PER_ID (+)
AND P.PER_ID = PC.PER_ID (+)
GROUP BY
P.PER_ID
, (P.CITY || ', ' || P.STATE || ',' || P.COUNTRY)
) P
WHERE
P.PER_ID = AP.PER_ID
AND AP.ACCT_ID = AC.ACCT_ID
AND AP.ACCT_ID = SA.ACCT_ID
AND AP.MAIN_CUST_SW = 'Y'
AND A.ACCT_ID = SA.ACCT_ID
AND A.ACCT_ID = AP.ACCT_ID
AND AC.CHAR_TYPE_CD = 'ACCTYPE'
AND AC.CHAR_VAL IN ('UOS', 'DEFAULT')
AND AC.ACCT_ID = SA.ACCT_ID
AND CL.LANGUAGE_CD = 'ENG'
AND A.ACCT_ID = AC.ACCT_ID
AND A.CUST_CL_CD = CL.CUST_CL_CD
AND SA.SA_ID = FT.SA_ID
AND FT.FREEZE_DTTM IS NOT NULL
GROUP BY
P.PER_ID
, CL.DESCR
, P.ENG_NAME
, P.ARA_NAME
, P.NATION
, P.ADDR
, ('Mob:' || NVL(P.MOB, '') || ', Home:' || NVL(P.HOME, '') || ', Bus.:' || NVL(P.BUS, '') || ', Fax:' || NVL(P.FAX, ''))
HAVING
SUM(FT.CUR_AMT) > 0
call count cpu elapsed disk query current rows
Parse 1 0.64 0.64 0 0 0 0
Execute 1 0.00 0.00 0 0 0 0
Fetch 304 353.09 430.04 21720 52997832 0 4543
total 306 353.73 430.69 21720 52997832 0 4543
Misses in library cache during parse: 1
Optimizer mode: CHOOSE
Parsing user id: 79 (CISADM)
Rows Row Source Operation
4543 FILTER (cr=52997832 pr=21720 pw=10311 time=430019418 us)
5412 HASH GROUP BY (cr=52997832 pr=21720 pw=10311 time=430015729 us)
199471 VIEW (cr=52997832 pr=21720 pw=10311 time=423392346 us)
199471 HASH GROUP BY (cr=52997832 pr=21720 pw=10311 time=423192867 us)
4013304 TABLE ACCESS BY INDEX ROWID CI_FT (cr=52997832 pr=11409 pw=0 time=140469508 us)
17717785 NESTED LOOPS (cr=49295470 pr=8987 pw=0 time=407554071 us)
13704480 NESTED LOOPS (cr=21818135 pr=7655 pw=0 time=287797921 us)
2782119 NESTED LOOPS OUTER (cr=3915432 pr=2950 pw=0 time=38953485 us)
571492 NESTED LOOPS OUTER (cr=2545763 pr=2711 pw=0 time=7433194 us)
286061 NESTED LOOPS OUTER (cr=2253263 pr=2671 pw=0 time=26607373 us)
123411 NESTED LOOPS (cr=1989056 pr=2642 pw=0 time=22711194 us)
123411 NESTED LOOPS (cr=1864959 pr=2642 pw=0 time=20860026 us)
123411 NESTED LOOPS (cr=1494040 pr=1754 pw=0 time=15553373 us)
243088 NESTED LOOPS (cr=29540 pr=1754 pw=0 time=10213331 us)
13227 TABLE ACCESS FULL CI_PER (cr=251 pr=49 pw=0 time=43331 us)
243088 INDEX RANGE SCAN XM150S1 (cr=29289 pr=1705 pw=0 time=6178159 us)(object id 97173)
123411 INLIST ITERATOR (cr=1464500 pr=0 pw=0 time=7220251 us)
123411 INDEX RANGE SCAN CM064S0 (cr=1464500 pr=0 pw=0 time=5631936 us)(object id 108631)
123411 TABLE ACCESS BY INDEX ROWID CI_ACCT (cr=370919 pr=888 pw=0 time=7241286 us)
123411 INDEX UNIQUE SCAN XM148P0 (cr=247508 pr=0 pw=0 time=1198649 us)(object id 97147)
123411 TABLE ACCESS BY INDEX ROWID CI_CUST_CL_L (cr=124097 pr=0 pw=0 time=1391837 us)
123411 INDEX UNIQUE SCAN XC523P0 (cr=686 pr=0 pw=0 time=595005 us)(object id 97745)
283749 TABLE ACCESS BY INDEX ROWID CI_PER_PHONE (cr=264207 pr=29 pw=0 time=3549713 us)
283749 INDEX RANGE SCAN XM172P0 (cr=125886 pr=4 pw=0 time=1307395 us)(object id 98733)
571492 INDEX RANGE SCAN XM171S2 (cr=292500 pr=40 pw=0 time=2976807 us)(object id 98728)
2777066 TABLE ACCESS BY INDEX ROWID CI_PER_CHAR (cr=1369669 pr=239 pw=0 time=23084761 us)
2777066 INDEX RANGE SCAN XM168P0 (cr=596156 pr=53 pw=0 time=7394319 us)(object id 98719)
13704480 TABLE ACCESS BY INDEX ROWID CI_SA (cr=17902703 pr=4705 pw=0 time=163320548 us)
13704480 INDEX RANGE SCAN XM199S1 (cr=5688247 pr=104 pw=0 time=51063061 us)(object id 98973)
4013304 INDEX RANGE SCAN CM112S1 (cr=27477335 pr=1332 pw=0 time=124063022 us)(object id 116797)
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
SQL*Net message to client 304 0.00 0.00
db file sequential read 11366 0.34 65.63
direct path write temp 1473 0.06 2.91
latch: cache buffers chains 17 0.00 0.00
db file scattered read 7 0.01 0.03
read by other session 2 0.00 0.00
direct path read temp 1473 0.03 6.85
SQL*Net message from client 304 0.02 2.74
SQL*Net more data to client 292 0.00 0.00
********************************************************************************Luckys
I've just realised that I mis-read part of your plan:
199471 HASH GROUP BY (cr=52997832 pr=21720 pw=10311 time=423192867 us)
4013304 TABLE ACCESS BY INDEX ROWID CI_FT (cr=52997832 pr=11409 pw=0 time=140469508 us)
17717785 NESTED LOOPS (cr=49295470 pr=8987 pw=0 time=407554071 us)The time component for a line is the time it supplies, plus the sum of the time from its direct descendents.
In this case I looked at the HASH GROUP BY and TABLE ACCESS and got a difference of about 283 seconds. In fact I should have taken more notice of the other lines in the plan - comparing the HASH GROUP BY with the NESTED LOOP for a difference of about 16 seconds and assuming that the time in the TABLE ACCESS line was not to be trusted. (See http://jonathanlewis.wordpress.com/2007/04/26/heisenberg/ for a couple of comments on the timing issue).
So the grouping is responsible for relatively little of the excess time - most of the time goes into the nested loop.
I shall be using the Hints as advised, when we say we
have to "rewrite the query"
given the current context excluding the HINTS, what
exactly should I be
considering in terms of query rewrite, what
additional intelligence I can add to the
query in question so that CBO produces a different
plan.
The main consideration is what the query is supposed to report. Compare this with the way the optimizer is running the query and see if it makes sense.
When are talking about high intermediate rows
processing are we referring to this
section of the plan?;
4013304 TABLE ACCESS BY INDEX ROWID CI_FT
(cr=52997832 pr=11409 pw=0 time=140469508 us)
17717785 NESTED LOOPS (cr=49295470 pr=8987
pw=0 time=407554071 us)
13704480 NESTED LOOPS (cr=21818135 pr=7655
pw=0 time=287797921 us)
2782119 NESTED LOOPS OUTER (cr=3915432
pr=2950 pw=0 time=38953485 us)
2777066 TABLE ACCESS BY INDEX ROWID
CI_PER_CHAR (cr=1369669 pr=239 pw=0 time=23084761
us)
2777066 INDEX RANGE SCAN XM168P0 (cr=596156
pr=53 pw=0 time=7394319 us)(object id 98719)
13704480 TABLE ACCESS BY INDEX ROWID CI_SA
(cr=17902703 pr=4705 pw=0 time=163320548 us)
13704480 INDEX RANGE SCAN XM199S1
(cr=5688247 pr=104 pw=0 time=51063061 us)(object id
98973)
4013304 INDEX RANGE SCAN CM112S1 (cr=27477335
pr=1332 pw=0 time=124063022 us)(object id 116797)
Correct - one of the nested loops returns 2.78M rows - but as you run the next join you end up collecting 13.7M entires from the next index and table. That step is responsible for quite a lot of your work and time (as is the following step where you USE the 13.7M rows to probe the next index/table combination). If the optimizer had not grown the data set by merging the P view earlier on, the data sizes would be significantly smaller at that point.
Your inline view looks as if it is trying to turn rows into columns (the max(decode()) trick) - which is why I think it might be a good idea to stop Oracle from merging the view. So, as I suggested, look at the query withouth that bit of complexity and work out a sensible way to walk through the tables - bearing in mind the statistics below and the available indexes, and the amount of data your predicates identify at each stage.
Moreover tables have been analyzed:
CI_ACCT 243068
CI_ACCT_CHAR 222320
CI_ACCT_PER 242971
CI_FT 794510
CI_PER 13227
CI_PER_CHAR 42555
CI_PER_PHONE 18488
CI_SA 1082301
Parameters:
optimizer_features_enable string 10.2.0.2
optimizer_index_caching integer 100
optimizer_index_cost_adj integer 1
Unless you've been given strict instructions by a 3rd-part supplier, those settings for the optimizer_index_caching and optimizer_index_cost_adj are particularly bad - especially in 10g. With those settings, the optimizer is quite likely to choose stupid plans with excessive use of indexes - and pick the wrong index while doing it.
It's not appropriate to fiddle with system parameters to address one query - but at some stage you need to rethink your entire set of parameter settings to do things the 10g way. See this note from the Optimizer Group: http://www.oracle.com/technology/products/bi/db/10g/pdf/twp_bidw_optimizer_10gr2_0208.pdf
Regards
Jonathan Lewis
http://jonathanlewis.wordpress.com
http://www.jlcomp.demon.co.uk
"The greatest enemy of knowledge is not ignorance,
it is the illusion of knowledge." Stephen Hawking. -
Huge long time direct path read temp, but pga size is enough, one block p3
Hi Gurus,
Can you please kindly provide some points on my below questions. thanks
my env
select * from v$version;
BANNER
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
PL/SQL Release 11.2.0.1.0 - Production
CORE 11.2.0.1.0 Production
TNS for Linux: Version 11.2.0.1.0 - Production
NLSRTL Version 11.2.0.1.0 - Production
OS: Linux 4 2.6.39-100.5.1.el5uek
session operation: update a partition which have 4 partitions and total 16G
session trace info:
the session keep at active status and waiting for below wait event for more than 70 hours, and os iostats and cpu are almost idle on most time.
WAIT #8: nam='direct path read temp' ela= 7615 file number=202 first dba=105072 block cnt=1 obj#=104719 tim=1344850223569499
WAIT #8: nam='direct path read temp' ela= 5989 file number=202 first dba=85264 block cnt=1 obj#=104719 tim=1344850392833257
WAIT #8: nam='direct path read temp' ela= 319 file number=202 first dba=85248 block cnt=1 obj#=104719 tim=1344850399563184
WAIT #8: nam='direct path read temp' ela= 358 file number=202 first dba=85232 block cnt=1 obj#=104719 tim=1344850406016899
WAIT #8: nam='direct path read temp' ela= 349 file number=202 first dba=85216 block cnt=1 obj#=104719 tim=1344850413023792
WAIT #8: nam='direct path read temp' ela= 7975 file number=202 first dba=85200 block cnt=1 obj#=104719 tim=1344850419495645
WAIT #8: nam='direct path read temp' ela= 331 file number=202 first dba=85184 block cnt=1 obj#=104719 tim=1344850426233450
WAIT #8: nam='direct path read temp' ela= 2641 file number=202 first dba=82880 block cnt=1 obj#=104719 tim=1344850432699800
pgastat:
NAME VALUE/1024/1024 UNIT
aggregate PGA target parameter 18432 bytes
aggregate PGA auto target 16523.1475 bytes
global memory bound 1024 bytes
total PGA inuse 75.7246094 bytes
total PGA allocated 162.411133 bytes
maximum PGA allocated 514.130859 bytes
total freeable PGA memory 64.625 bytes
PGA memory freed back to OS 40425.1875 bytes
total PGA used for auto workareas 2.75195313 bytes
maximum PGA used for auto workareas 270.407227 bytes
total PGA used for manual workareas 0 bytes
NAME VALUE/1024/1024 UNIT
maximum PGA used for manual workareas 24.5429688 bytes
bytes processed 110558.951 bytes
extra bytes read/written 15021.2559 bytes
Most operation in PGA via query on V$SQL_WORKAREA_ACTIVE
IDX maintainenance (sort)
My questions:
1. why 'direct path read temp' just read one block every time, my understanding is this event can read one block and multiple blocks at one read call, why it keep read one block in my session?
2. my pga size is big enough, why this operation can not be treated with in PGA memory, instead of read block from disk into temp tablespace?
Thanks for you inputs.
Roy951241 wrote:
since the session(which was from hard code application) is completed.First of all, you showed wait events from sql trace in the first post. Is the tracing was disabled in the latest execution?
>
I just generated the AWR for that period, as get long elapsed time SQL as following
Elapsed Time (s) Executions Elapsed Time per Exec (s) %Total %CPU %IO SQL Id
3,075.35 0 85.10 91.03 8.68 duhz2wtduz709
524.11 1 524.11 14.50 99.29 0.30 3cpa9fxny9j35
so I get execution plan as below for these two SQL,
select * from table(dbms_xplan.display_awr('&v_sql_id')); duhz2wtduz709
PLAN_TABLE_OUTPUT
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
| 0 | UPDATE STATEMENT | | | | 4 (100)| |
| 1 | UPDATE | WORK_PAY_LINE | | | | |
| 2 | INDEX RANGE SCAN| WORK_PAY_LINE | 1 | 37 | 3 (0)| 00:00:01 |
Note
- automatic DOP: Computed Degree of Parallelism is 1 because of parallel thresholdI am not sure the why elapsed time in AWR is different with time in execution plan. Column "Time" in an execution plan is estimated time. In this execution plan Oracle expects to get 1 row, estimated time is 1 sec.
So, you need to check why estimated cardinality is such low, check statistics on the table WORK_PAY_LINE.
You update 10Gb from 16Gb table via Index Range Scan, it looks inefficient here by two reasons:
1. when a table updated via Index Range Scan optimized index maintenance is used. As a result some amount (significant in your case) of workareas is required. Required size depends on size and number of updated indexes and "global memory bound", 1Gb in your case.
2. if required table buffers will not be found in the cache it will be read from disk by single block reads. If you would use Full Table Scan then buffers for update most likely will be found in the cache because before it read by multiblock reads during Full Table Scan.
Figures from your AWR indicate, that only ~ 9% the session waited for I/O and 91% it worked and used CPU
Elapsed Time (s) Executions Elapsed Time per Exec (s) %Total %CPU %IO SQL Id
3,075.35 0 85.10 91.03 8.68 duhz2wtduz709 This amount of CPU time partially required for UPDATE 10Gb of data, partially for sorting during optimized index maintenance.
I would propose to use Table Full Scan here.
Also you can play around and create fake trigger on update, it will make impossible to use optimized index maintenance, usual index maintenance will be used. As a result you can check the same update with the same execution plan (with Index Range Scan) but without optimized index maintenance and "direct path .. temp" wait events.
Alexander Anokhin
http://alexanderanokhin.wordpress.com/ -
Oracle SQL and PL/SQL interview questions.
Can anyone forward me all Oracle SQL and PL/SQL Interview questions and answers asap.
Many Thanks.
BbaDear Pal
I not sure all the all answers are correct. I got one mail couple yrs back. I am just sharing mail contents. Kindly keep question and compare answers.
1 Which is more faster - IN or EXISTS?
EXISTS is more faster than IN because EXISTS returns a Boolean value whereas IN returns a value.
2 Which datatype is used for storing graphics and images?
LONG RAW data type is used for storing BLOB's (binary large objects).
3 When do you use WHERE clause and when do you use HAVING clause?
HAVING clause is used when you want to specify a condition for a group function and it is written after GROUP BY clause. The WHERE clause is used when you want to specify a condition for columns, single row functions except group functions and it is written before GROUP BY clause if it is used.
4 What WHERE CURRENT OF clause does in a cursor?
LOOPSELECT num_credits INTO v_numcredits FROM classesWHERE dept=123 and course=101;UPDATE studentsSET current_credits=current_credits+v_numcreditsWHERE CURRENT OF X;END LOOPCOMMIT;END;
5 What should be the return type for a cursor variable.Can we use a scalar data type as return type?
The return type for a cursor must be a record type.It can be declared explicitly as a user-defined or %ROWTYPE can be used. eg TYPE t_studentsref IS REF CURSOR RETURN students%ROWTYPE
6 What is use of a cursor variable? How it is defined?
A cursor variable is associated with different statements at run time, which can hold different values at run time. Static cursors can only be associated with one run time query. A cursor variable is reference type (like a pointer in C).Declaring a cursor variable:TYPE type_name IS REF CURSOR RETURN return_type type_name is the name of the reference type,return_type is a record type indicating the types of the select list that will eventually be returned by the cursor variable.
7 What is the purpose of a cluster?
Oracle does not allow a user to specifically locate tables, since that is a part of the function of the RDBMS. However, for the purpose of increasing performance, oracle allows a developer to create a CLUSTER. A CLUSTER provides a means for storing data from different tables together for faster retrieval than if the table placement were left to the RDBMS.
8 What is the maximum buffer size that can be specified using the DBMS_OUTPUT.ENABLE function?
1,000,00
9 What is syntax for dropping a procedure and a function .Are these operations possible?
Drop Procedure procedure_nameDrop Function function_name
10 What is OCI. What are its uses?
Oracle Call Interface is a method of accesing database from a 3GL program. Uses--No precompiler is required,PL/SQL blocks are executed like other DML statements. The OCI library provides· -functions to parse SQL statemets· -bind input variables· -bind output variables· -execute statements· -fetch the results
11 What is difference between UNIQUE and PRIMARY KEY constraints?
A table can have only one PRIMARY KEY whereas there can be any number of UNIQUE keys. The columns that compose PK are automatically define NOT NULL, whereas a column that compose a UNIQUE is not automatically defined to be mandatory must also specify the column is NOT NULL.
12 What is difference between SUBSTR and INSTR?
SUBSTR returns a specified portion of a string eg SUBSTR('BCDEF',4) output BCDEINSTR provides character position in which a pattern is found in a string. eg INSTR('ABC-DC-F','-',2) output 7 (2nd occurence of '-')
13 What is difference between SQL and SQL*PLUS?
SQL*PLUS is a command line tool where as SQL and PL/SQL language interface and reporting tool. Its a command line tool that allows user to type SQL commands to be executed directly against an Oracle database. SQL is a language used to query the relational database(DML,DCL,DDL). SQL*PLUS commands are used to format query result, Set options, Edit SQL commands and PL/SQL.
14 What is difference between Rename and Alias?
Rename is a permanent name given to a table or column whereas Alias is a temporary name given to a table or column which do not exist once the SQL statement is executed.
15 What is difference between a formal and an actual parameter?
The variables declared in the procedure and which are passed, as arguments are called actual, the parameters in the procedure declaration. Actual parameters contain the values that are passed to a procedure and receive results. Formal parameters are the placeholders for the values of actual parameters
16 What is an UTL_FILE.What are different procedures and functions associated with it?
UTL_FILE is a package that adds the ability to read and write to operating system files. Procedures associated with it are FCLOSE, FCLOSE_ALL and 5 procedures to output data to a file PUT, PUT_LINE, NEW_LINE, PUTF, FFLUSH.PUT, FFLUSH.PUT_LINE,FFLUSH.NEW_LINE. Functions associated with it are FOPEN, ISOPEN.
17 What is a view ?
A view is stored procedure based on one or more tables, its a virtual table.
18 What is a pseudo column. Give some examples?
It is a column that is not an actual column in the table.eg USER, UID, SYSDATE, ROWNUM, ROWID, NULL, AND LEVEL.
19 What is a OUTER JOIN?
Outer Join--Its a join condition used where you can query all the rows of one of the tables in the join condition even though they dont satisfy the join condition.
20 What is a cursor?
Oracle uses work area to execute SQL statements and store processing information PL/SQL construct called a cursor lets you name a work area and access its stored information A cursor is a mechanism used to fetch more than one row in a Pl/SQl block.
21 What is a cursor for loop?
Cursor For Loop is a loop where oracle implicitly declares a loop variable, the loop index that of the same record type as the cursor's record.
22 What are various privileges that a user can grant to another user?
· SELECT· CONNECT· RESOURCES
23 What are various constraints used in SQL?
· NULL· NOT NULL· CHECK· DEFAULT
24 What are ORACLE PRECOMPILERS?
Using ORACLE PRECOMPILERS, SQL statements and PL/SQL blocks can be contained inside 3GL programs written in C,C++,COBOL,PASCAL, FORTRAN,PL/1 AND ADA.The Precompilers are known as Pro*C,Pro*Cobol,...This form of PL/SQL is known as embedded pl/sql,the language in which pl/sql is embedded is known as the host language. The prcompiler translates the embedded SQL and pl/sql ststements into calls to the precompiler runtime library.The output must be compiled and linked with this library to creater an executable.
25 What are different Oracle database objects?
· TABLES· VIEWS· INDEXES· SYNONYMS· SEQUENCES· TABLESPACES etc
26 What are different modes of parameters used in functions and procedures?
· IN· OUT· INOUT
27 What are cursor attributes?
· %ROWCOUNT· %NOTFOUND· %FOUND· %ISOPEN
28 What a SELECT FOR UPDATE cursor represent. [ANSWER]SELECT......FROM......FOR......UPDATE[OF column-reference][NOWAIT] The processing done in a fetch loop modifies the rows that have been retrieved by the cursor. A convenient way of modifying the rows is done by a method with two parts: the FOR UPDATE clause in the cursor declaration, WHERE CURRENT OF CLAUSE in an UPDATE or declaration statement.
29 There is a string 120000 12 0 .125 , how you will find the position of the decimal place?
INSTR('120000 12 0 .125',1,'.')output 13
30 There is a % sign in one field of a column. What will be the query to find it?
'' Should be used before '%'.
31 Suppose a customer table is having different columns like customer no, payments.What will be the query to select top three max payments?
SELECT customer_no, payments from customer C1
WHERE 3<=(SELECT COUNT(*) from customer C2
WHERE C1.payment <= C2.payment)
32 minvalue.sql Select the Nth lowest value from a table
select level, min('col_name') from my_table where level = '&n' connect by prior ('col_name') <
'col_name')
group by level;
Example:
Given a table called emp with the following columns:
-- id number
-- name varchar2(20)
-- sal number
-- For the second lowest salary:
-- select level, min(sal) from emp
-- where level=2
-- connect by prior sal < sal
-- group by level
33 maxvalue.sql Select the Nth Highest value from a table
select level, max('col_name') from my_table where level = '&n' connect by prior ('col_name') >
'col_name')
group by level;
Example:
Given a table called emp with the following columns:
-- id number
-- name varchar2(20)
-- sal number
-- For the second highest salary:
-- select level, max(sal) from emp
-- where level=2
-- connect by prior sal > sal
-- group by level
34 How you will avoid your query from using indexes?
SELECT * FROM emp
Where emp_no+' '=12345;
i.e you have to concatenate the column name with space within codes in the where condition.
SELECT /*+ FULL(a) */ ename, emp_no from emp
where emp_no=1234;
i.e using HINTS
35 How you will avoid duplicating records in a query?
By using DISTINCT
36 How you were passing cursor variables in PL/SQL 2.2?
In PL/SQL 2.2 cursor variables cannot be declared in a package.This is because the storage for a cursor variable has to be allocated using Pro*C or OCI with version 2.2, the only means of passing a cursor variable to a PL/SQL block is via bind variable or a procedure parameter.
37 How you open and close a cursor variable.Why it is required?
OPEN cursor variable FOR SELECT...Statement
CLOSE cursor variable In order to associate a cursor variable with a particular SELECT statement OPEN syntax is used. In order to free the resources used for the query CLOSE statement is used.
38 How will you delete duplicating rows from a base table?
delete from table_name where rowid not in (select max(rowid) from table group by duplicate_values_field_name); or
delete duplicate_values_field_name dv from table_name ta where rowid <(select min(rowid) from table_name tb where ta.dv=tb.dv);
39 How do you find the numbert of rows in a Table ?
A bad answer is count them (SELECT COUNT(*) FROM table_name)
A good answer is :-
'By generating SQL to ANALYZE TABLE table_name COUNT STATISTICS by querying Oracle System Catalogues (e.g. USER_TABLES or ALL_TABLES).
The best answer is to refer to the utility which Oracle released which makes it unnecessary to do ANALYZE TABLE for each Table individually.
40 Find out nth highest salary from emp table
SELECT DISTINCT (a.sal) FROM EMP A WHERE &N = (SELECT COUNT (DISTINCT (b.sal)) FROM EMP B WHERE a.sal<=b.sal);
For Eg:-
Enter value for n: 2
SAL
3700
41 Display the records between two range?
select rownum, empno, ename from emp where rowid in (select rowid from emp where rownum <=&upto minus select rowid from emp where rownum<&Start);
42 Display the number value in Words?
SQL> select sal, (to_char(to_date(sal,'j'), 'jsp'))
from emp;
the output like,
SAL (TO_CHAR(TO_DATE(SAL,'J'),'JSP'))
800 eight hundred
1600 one thousand six hundred
1250 one thousand two hundred fifty
If you want to add some text like, Rs. Three Thousand only.
SQL> select sal "Salary ",
(' Rs. '|| (to_char(to_date(sal,'j'), 'Jsp'))|| ' only.'))
"Sal in Words" from emp
Salary Sal in Words
800 Rs. Eight Hundred only.
1600 Rs. One Thousand Six Hundred only.
1250 Rs. One Thousand Two Hundred Fifty only.
43 Display Odd/ Even number of records
Odd number of records:
select * from emp where (rowid,1) in (select rowid, mod(rownum,2) from emp);
Output:-
1
3
5
Even number of records:
select * from emp where (rowid,0) in (select rowid, mod(rownum,2) from emp)
Output:-
2
4
6
44 Difference between procedure and function.
Functions are named PL/SQL blocks that return a value and can be called with arguments procedure a named block that can be called with parameter. A procedure all is a PL/SQL statement by itself, while a Function call is called as part of an expression.
45 Difference between NO DATA FOUND and %NOTFOUND
NO DATA FOUND is an exception raised only for the SELECT....INTO statements when the where clause of the querydoes not match any rows. When the where clause of the explicit cursor does not match any rows the %NOTFOUND attribute is set to TRUE instead.
46 Difference between database triggers and form triggers?
Data base trigger(DBT) fires when a DML operation is performed on a data base table. Form trigger(FT) Fires when user presses a key or navigates between fields on the screen
Can be row level or statement level No distinction between row level and statement level.
Can manipulate data stored in Oracle tables via SQL Can manipulate data in Oracle tables as well as variables in forms.
Can be fired from any session executing the triggering DML statements. Can be fired only from the form that define the trigger.
Can cause other database triggers to fire.Can cause other database triggers to fire, but not other form triggers.
47 Difference between an implicit & an explicit cursor.
PL/SQL declares a cursor implicitly for all SQL data manipulation statements, including quries that return only one row. However,queries that return more than one row you must declare an explicit cursor or use a cursor FOR loop.
Explicit cursor is a cursor in which the cursor name is explicitly assigned to a SELECT statement via the CURSOR...IS statement. An implicit cursor is used for all SQL statements Declare, Open, Fetch, Close. An explicit cursors are used to process multirow SELECT statements An implicit cursor is used to process INSERT, UPDATE, DELETE and single row SELECT. .INTO statements.
48 Can you use a commit statement within a database trigger?
No.
49 Can the default values be assigned to actual parameters?
Yes
50 Can cursor variables be stored in PL/SQL tables.If yes how. If not why?
No, a cursor variable points a row which cannot be stored in a two-dimensional PL/SQL table.
51 Can a primary key contain more than one columns?
Yes
52 Can a function take OUT parameters. If not why?
No. A function has to return a value,an OUT parameter cannot return a value.
53 What are various joins used while writing SUBQUERIES?
Self join-Its a join foreign key of a table references the same table. Outer Join--Its a join condition used where One can query all the rows of one of the tables in the join condition even though they don't satisfy the join condition.
Equi-join--Its a join condition that retrieves rows from one or more tables in which one or more columns in one table are equal to one or more columns in the second table.
54 Differentiate between TRUNCATE and DELETE
TRUNCATE deletes much faster than DELETE
TRUNCATE
DELETE
It is a DDL statement It is a DML statement
It is a one way trip,cannot ROLLBACK One can Rollback
Doesn't have selective features (where clause) Has
Doesn't fire database triggers Does
It requires disabling of referential constraints. Does not require
1 What is PL/SQL ?
PL/SQL is a procedural language that has both interactive SQL and procedural programming language constructs such as iteration, conditional branching.
2 Write the order of precedence for validation of a column in a table ?
I. done using Database triggers.
ii. done using Integarity Constraints.
I & ii.
Exception :
3 Where the Pre_defined_exceptions are stored ?
In the standard package.
Procedures, Functions & Packages ;
4 What are % TYPE and % ROWTYPE ? What are the advantages of using these over datatypes?
% TYPE provides the data type of a variable or a database column to that variable.
% ROWTYPE provides the record type that represents a entire row of a table or view or columns selected in the cursor.
The advantages are : I. Need not know about variable's data type
ii. If the database definition of a column in a table changes, the data type of a variable changes accordingly.
5 What will happen after commit statement ?
Cursor C1 is
Select empno,
ename from emp;
Begin
open C1; loop
Fetch C1 into
eno.ename;
Exit When
C1 %notfound;-----
commit;
end loop;
end;
The cursor having query as SELECT .... FOR UPDATE gets closed after COMMIT/ROLLBACK.
The cursor having query as SELECT.... does not get closed even after COMMIT/ROLLBACK.
6 What is the basic structure of PL/SQL ?
PL/SQL uses block structure as its basic structure. Anonymous blocks or nested blocks can be used in PL/SQL.
7 What is Raise_application_error ?
Raise_application_error is a procedure of package DBMS_STANDARD which allows to issue an user_defined error messages from stored sub-program or database trigger.
8 What is Pragma EXECPTION_INIT ? Explain the usage ?
The PRAGMA EXECPTION_INIT tells the complier to associate an exception with an oracle error. To get an error message of a specific oracle error.
e.g. PRAGMA EXCEPTION_INIT (exception name, oracle error number)
9 What is PL/SQL table ?
Objects of type TABLE are called "PL/SQL tables", which are modeled as (but not the same as) database tables, PL/SQL tables use a primary PL/SQL tables can have one column and a primary key.
Cursors
10 What is Overloading of procedures ?
The Same procedure name is repeated with parameters of different datatypes and parameters in different positions, varying number of parameters is called overloading of procedures.
e.g. DBMS_OUTPUT put_line
What is a package ? What are the advantages of packages ?
11 What is difference between a PROCEDURE & FUNCTION ?
A FUNCTION is always returns a value using the return statement.
A PROCEDURE may return one or more values through parameters or may not return at all.
12 What is difference between a Cursor declared in a procedure and Cursor declared in a package specification ?
A cursor declared in a package specification is global and can be accessed by other procedures or procedures in a package.
A cursor declared in a procedure is local to the procedure that can not be accessed by other procedures.
13 What is difference between % ROWTYPE and TYPE RECORD ?
% ROWTYPE is to be used whenever query returns a entire row of a table or view.
TYPE rec RECORD is to be used whenever query returns columns of different
table or views and variables.
E.g. TYPE r_emp is RECORD (eno emp.empno% type,ename emp ename %type
e_rec emp% ROWTYPE
cursor c1 is select empno,deptno from emp;
e_rec c1 %ROWTYPE.
14 What is an Exception ? What are types of Exception ?
Exception is the error handling part of PL/SQL block. The types are Predefined and user defined. Some of Predefined exceptions are.
CURSOR_ALREADY_OPEN
DUP_VAL_ON_INDEX
NO_DATA_FOUND
TOO_MANY_ROWS
INVALID_CURSOR
INVALID_NUMBER
LOGON_DENIED
NOT_LOGGED_ON
PROGRAM-ERROR
STORAGE_ERROR
TIMEOUT_ON_RESOURCE
VALUE_ERROR
ZERO_DIVIDE
OTHERS.
15 What is a stored procedure ?
A stored procedure is a sequence of statements that perform specific function.
16 What is a database trigger ? Name some usages of database trigger ?
Database trigger is stored PL/SQL program unit associated with a specific database table. Usages are Audit data modifications, Log events transparently, Enforce complex business rules Derive column values automatically, Implement complex security authorizations. Maintain replicate tables.
17 What is a cursor for loop ?
Cursor for loop implicitly declares %ROWTYPE as loop index,opens a cursor, fetches rows of values from active set into fields in the record and closes
when all the records have been processed.
eg. FOR emp_rec IN C1 LOOP
salary_total := salary_total +emp_rec sal;
END LOOP;
18 What is a cursor ? Why Cursor is required ?
Cursor is a named private SQL area from where information can be accessed. Cursors are required to process rows individually for queries returning multiple rows.
19 What happens if a procedure that updates a column of table X is called in a database trigger of the same table ?
Mutation of table occurs.
20 What are two virtual tables available during database trigger execution ?
The table columns are referred as OLD.column_name and NEW.column_name.
For triggers related to INSERT only NEW.column_name values only available.
For triggers related to UPDATE only OLD.column_name NEW.column_name values only available.
For triggers related to DELETE only OLD.column_name values only available.
21 What are two parts of package ?
The two parts of package are PACKAGE SPECIFICATION & PACKAGE BODY.
Package Specification contains declarations that are global to the packages and local to the schema.
Package Body contains actual procedures and local declaration of the procedures and cursor declarations.
22 What are the two parts of a procedure ?
Procedure Specification and Procedure Body.
23 What are the return values of functions SQLCODE and SQLERRM ?
SQLCODE returns the latest code of the error that has occurred.
SQLERRM returns the relevant error message of the SQLCODE.
24 What are the PL/SQL Statements used in cursor processing ?
DECLARE CURSOR cursor name, OPEN cursor name, FETCH cursor name INTO or Record types, CLOSE cursor name.
25 What are the modes of parameters that can be passed to a procedure ?
IN,OUT,IN-OUT parameters.
26 What are the datatypes a available in PL/SQL ?
Some scalar data types such as NUMBER, VARCHAR2, DATE, CHAR, LONG, BOOLEAN.
Some composite data types such as RECORD & TABLE.
27 What are the cursor attributes used in PL/SQL ?
%ISOPEN - to check whether cursor is open or not
% ROWCOUNT - number of rows fetched/updated/deleted.
% FOUND - to check whether cursor has fetched any row. True if rows are fetched.
% NOT FOUND - to check whether cursor has fetched any row. True if no rows are featched.
These attributes are proceeded with SQL for Implicit Cursors and with Cursor name for Explicit Cursors.
28 What are the components of a PL/SQL Block ?
Declarative part, Executable part and Exception part.
Datatypes PL/SQL
29 What are the components of a PL/SQL block ?
A set of related declarations and procedural statements is called block.
30 What are advantages fo Stored Procedures /
Extensibility,Modularity, Reusability, Maintainability and one time compilation.
1 What is PL/SQL ?
PL/SQL is a procedural language that has both interactive SQL and procedural programming language constructs such as iteration, conditional branching.
2 Write the order of precedence for validation of a column in a table ?
I. done using Database triggers.
ii. done using Integarity Constraints.
I & ii.
Exception :
3 Where the Pre_defined_exceptions are stored ?
In the standard package.
Procedures, Functions & Packages ;
4 What are % TYPE and % ROWTYPE ? What are the advantages of using these over datatypes?
% TYPE provides the data type of a variable or a database column to that variable.
% ROWTYPE provides the record type that represents a entire row of a table or view or columns selected in the cursor.
The advantages are : I. Need not know about variable's data type
ii. If the database definition of a column in a table changes, the data type of a variable changes accordingly.
5 What will happen after commit statement ?
Cursor C1 is
Select empno,
ename from emp;
Begin
open C1; loop
Fetch C1 into
eno.ename;
Exit When
C1 %notfound;-----
commit;
end loop;
end;
The cursor having query as SELECT .... FOR UPDATE gets closed after COMMIT/ROLLBACK.
The cursor having query as SELECT.... does not get closed even after COMMIT/ROLLBACK.
6 What is the basic structure of PL/SQL ?
PL/SQL uses block structure as its basic structure. Anonymous blocks or nested blocks can be used in PL/SQL.
7 What is Raise_application_error ?
Raise_application_error is a procedure of package DBMS_STANDARD which allows to issue an user_defined error messages from stored sub-program or database trigger.
8 What is Pragma EXECPTION_INIT ? Explain the usage ?
The PRAGMA EXECPTION_INIT tells the complier to associate an exception with an oracle error. To get an error message of a specific oracle error.
e.g. PRAGMA EXCEPTION_INIT (exception name, oracle error number)
9 What is PL/SQL table ?
Objects of type TABLE are called "PL/SQL tables", which are modeled as (but not the same as) database tables, PL/SQL tables use a primary PL/SQL tables can have one column and a primary key.
Cursors
10 What is Overloading of procedures ?
The Same procedure name is repeated with parameters of different datatypes and parameters in different positions, varying number of parameters is called overloading of procedures.
e.g. DBMS_OUTPUT put_line
What is a package ? What are the advantages of packages ?
11 What is difference between a PROCEDURE & FUNCTION ?
A FUNCTION is always returns a value using the return statement.
A PROCEDURE may return one or more values through parameters or may not return at all.
12 What is difference between a Cursor declared in a procedure and Cursor declared in a package specification ?
A cursor declared in a package specification is global and can be accessed by other procedures or procedures in a package.
A cursor declared in a procedure is local to the procedure that can not be accessed by other procedures.
13 What is difference between % ROWTYPE and TYPE RECORD ?
% ROWTYPE is to be used whenever query returns a entire row of a table or view.
TYPE rec RECORD is to be used whenever query returns columns of different
table or views and variables.
E.g. TYPE r_emp is RECORD (eno emp.empno% type,ename emp ename %type
e_rec emp% ROWTYPE
cursor c1 is select empno,deptno from emp;
e_rec c1 %ROWTYPE.
14 What is an Exception ? What are types of Exception ?
Exception is the error handling part of PL/SQL block. The types are Predefined and user defined. Some of Predefined exceptions are.
CURSOR_ALREADY_OPEN
DUP_VAL_ON_INDEX
NO_DATA_FOUND
TOO_MANY_ROWS
INVALID_CURSOR
INVALID_NUMBER
LOGON_DENIED
NOT_LOGGED_ON
PROGRAM-ERROR
STORAGE_ERROR
TIMEOUT_ON_RESOURCE
VALUE_ERROR
ZERO_DIVIDE
OTHERS.
15 What is a stored procedure ?
A stored procedure is a sequence of statements that perform specific function.
16 What is a database trigger ? Name some usages of database trigger ?
Database trigger is stored PL/SQL program unit associated with a specific database table. Usages are Audit data modifications, Log events transparently, Enforce complex business rules Derive column values automatically, Implement complex security authorizations. Maintain replicate tables.
17 What is a cursor for loop ?
Cursor for loop implicitly declares %ROWTYPE as loop index,opens a cursor, fetches rows of values from active set into fields in the record and closes
when all the records have been processed.
eg. FOR emp_rec IN C1 LOOP
salary_total := salary_total +emp_rec sal;
END LOOP;
18 What is a cursor ? Why Cursor is required ?
Cursor is a named private SQL area from where information can be accessed. Cursors are required to process rows individually for queries returning multiple rows.
19 What happens if a procedure that updates a column of table X is called in a database trigger of the same table ?
Mutation of table occurs.
20 What are two virtual tables available during database trigger execution ?
The table columns are referred as OLD.column_name and NEW.column_name.
For triggers related to INSERT only NEW.column_name values only available.
For triggers related to UPDATE only OLD.column_name NEW.column_name values only available.
For triggers related to DELETE only OLD.column_name values only available.
21 What are two parts of package ?
The two parts of package are PACKAGE SPECIFICATION & PACKAGE BODY.
Package Specification contains declarations that are global to the packages and local to the schema.
Package Body contains actual procedures and local declaration of the procedures and cursor declarations.
22 What are the two parts of a procedure ?
Procedure Specification and Procedure Body.
23 What are the return values of functions SQLCODE and SQLERRM ?
SQLCODE returns the latest code of the error that has occurred.
SQLERRM returns the relevant error message of the SQLCODE.
24 What are the PL/SQL Statements used in cursor processing ?
DECLARE CURSOR cursor name, OPEN cursor name, FETCH cursor name INTO or Record types, CLOSE cursor name.
25 What are the modes of parameters that can be passed to a procedure ?
IN,OUT,IN-OUT parameters.
26 What are the datatypes a available in PL/SQL ?
Some scalar data types such as NUMBER, VARCHAR2, DATE, CHAR, LONG, BOOLEAN.
Some composite data types such as RECORD & TABLE.
27 What are the cursor attributes used in PL/SQL ?
%ISOPEN - to check whether cursor is open or not
% ROWCOUNT - number of rows fetched/updated/deleted.
% FOUND - to check whether cursor has fetched any row. True if rows are fetched.
% NOT FOUND - to check whether cursor has fetched any row. True if no rows are featched.
These attributes are proceeded with SQL for Implicit Cursors and with Cursor name for Explicit Cursors.
28 What are the components of a PL/SQL Block ?
Declarative part, Executable part and Exception part.
Datatypes PL/SQL
29 What are the components of a PL/SQL block ?
A set of related declarations and procedural statements is called block.
30 What are advantages fo Stored Procedures /
Extensibility,Modularity, Reusability, Maintainability and one time compilation.
31 Name the tables where characteristics of Package, procedure and functions are stored ?
User_objects, User_Source and User_error.
32 Is it possible to use Transaction control Statements such a ROLLBACK or COMMIT in Database Trigger ? Why ?
It is not possible. As triggers are defined for each table, if you use COMMIT of ROLLBACK in a trigger, it affects logical transaction processing.
33 How packaged procedures and functions are called from the following?
a. Stored procedure or anonymous block
b. an application program such a PRC C, PRO COBOL
c. SQL *PLUS
a. PACKAGE NAME.PROCEDURE NAME (parameters);
variable := PACKAGE NAME.FUNCTION NAME (arguments);
EXEC SQL EXECUTE
b.
BEGIN
PACKAGE NAME.PROCEDURE NAME (parameters)
variable := PACKAGE NAME.FUNCTION NAME (arguments);
END;
END EXEC;
c. EXECUTE PACKAGE NAME.PROCEDURE if the procedures does not have any
out/in-out parameters. A function can not be called.
34 How many types of database triggers can be specified on a table ? What are they ?
Insert Update Delete
Before Row o.k. o.k. o.k.
After Row o.k. o.k. o.k.
Before Statement o.k. o.k. o.k.
After Statement o.k. o.k. o.k.
If FOR EACH ROW clause is specified, then the trigger for each Row affected by the statement.
If WHEN clause is specified, the trigger fires according to the returned Boolean value.
35 Give the structure of the procedure ?
PROCEDURE name (parameter list.....)
is
local variable declarations
BEGIN
Executable statements.
Exception.
exception handlers
end;
36 Give the structure of the function ?
FUNCTION name (argument list .....) Return datatype is
local variable declarations
Begin
executable statements
Exception
execution handlers
End;
37 Explain the usage of WHERE CURRENT OF clause in cursors ?
WHERE CURRENT OF clause in an UPDATE,DELETE statement refers to the latest row fetched from a cursor.
Database Triggers
38 Explain the two type of Cursors ?
There are two types of cursors, Implicit Cursor and Explicit Cursor.
PL/SQL uses Implicit Cursors for queries.
User defined cursors are called Explicit Cursors. They can be declared and used.
39 Explain how procedures and functions are called in a PL/SQL block ?
Function is called as part of an expression.
sal := calculate_sal ('a822');
procedure is called as a PL/SQL statement
calculate_bonus ('A822');
Programmatic Constructs
Last Update: September 06, 2004
1 What are the different types of PL/SQL program units that can be defined and stored in ORACLE database ?
Procedures and Functions,Packages and Database Triggers.
2 What are the differences between Database Trigger and Integrity constraints ?
A declarative integrity constraint is a statement about the database that is always true. A constraint applies to existing data in the table and any statement that manipulates the table.
A trigger does not apply to data loaded before the definition of the trigger, therefore, it does not guarantee all data in a table conforms to the rules established by an associated trigger.
A trigger can be used to enforce transitional constraints where as a declarative integrity constraint cannot be used.
3 What is difference between Procedures and Functions ?
A Function returns a value to the caller where as a Procedure does not.
4 What is Database Trigger ?
A Database Trigger is procedure (set of SQL and PL/SQL statements) that is automatically executed as a result of an insert in,update to, or delete from a table.
5 What is a Procedure ?
A Procedure consist of a set of SQL and PL/SQL statements that are grouped together as a unit to solve a specific problem or perform a set of related tasks.
6 What is a Package ?
A Package is a collection of related procedures, functions, variables and other package constructs together as a unit in the database.
7 What are the uses of Database Trigger ?
Database triggers can be used to automatic data generation, audit data modifications, enforce complex Integrity constraints, and customize complex security authorizations.
8 What are the advantages of having a Package ?
Increased functionality (for example,global package variables can be declared and used by any proecdure in the package) and performance (for example all objects of the package are parsed compiled, and loaded into memory once)
1 With which function of summary item is the compute at options required?
percentage of total functions.
2 Why is it preferable to create a fewer no. of queries in the data model?
Because for each query, report has to open a separate cursor and has to rebind, execute and fetch data.
3 Why is a Where clause faster than a group filter or a format trigger?
Because, in a where clause the condition is applied during data retrieval than after retrieving the data.
4 Which parameter can be used to set read level consistency across multiple queries?
Read only.
5 Which of the two views should objects according to possession?
view by structure.
6 Which of the above methods is the faster method?
performing the calculation in the query is faster.
7 Where is the external query executed at the client or the server?
At the server.
8 Where is a procedure return in an external pl/sql library executed at the client or at the server?
At the client.
9 When do you use data parameter type?
When the value of a data parameter being passed to a called product is always the name of the record group defined in the current form. Data parameters are used to pass data to produts invoked with the run_product built-in subprogram.
10 When a form is invoked with call_form, Does oracle forms issues a save point?
Yes
11 What are the important difference between property clause and visual attributes?
Named visual attributes differ only font, color & pattern attributes, property clauses can contain this and any other properties. You can change the appearance of objects at run time by changing the named visual attributes programmatically , property clause assignments cannot be changed programmatically. When an object is inheriting from both a property clause and named visual attribute, the named visual attribute settings take precedence, and any visual attribute properties in the class are ignored.
12 What use of command line parameter cmd file?
It is a command line argument that allows you to specify a file that contain a set of arguments for r20run.
13 What is WHEN-Database-record trigger?
Fires when oracle forms first marks a record as an insert or an update. The trigger fires as soon as oracle forms determines through validation that the record should be processed by the next post or commit as an insert or update. c generally occurs only when the operators modifies the first item in the record, and after the operator attempts to navigate out of the item.
14 What is use of term?
The term file which key is correspond to which oracle report functions.
15 What is trigger associated with the timer?
When-timer-expired.
16 What is the use of transactional triggers?
Using transactional triggers we can control or modify the default functionality of the oracle forms.
17 What is the use of place holder column?
A placeholder column is used to hold calculated values at a specified place rather than allowing is to appear in the actual row where it has to appear.
18 What is the use of image_zoom built-in?
To manipulate images in image items.
19 What is the use of hidden column?
A hidden column is used to when a column has to embed into boilerplate text.
20 What is the use of break group?
A break group is used to display one record for one group ones. While multiple related records in other group can be displayed.
21 What is the remove on exit property?
For a modelless window, it determines whether oracle forms hides the window automatically when the operators navigates to an item in the another window.
22 What is the purpose of the product order option in the column property sheet?
To specify the order of individual group evaluation in a cross products.
23 What is the maximum no of chars the parameter can store?
The maximum no of chars the parameter can store is only valid for char parameters, which can be upto 64K. No parameters default to 23Bytes and Date parameter default to 7Bytes.
24 What is the main diff. bet. Reports 2.0 & Reports 2.5?
Report 2.5 is object oriented.
25 What is the frame & repeating frame?
A frame is a holder for a group of fields. A repeating frame is used to display a set of records when the no. of records that are to displayed is not known before.
26 What is the difference between OLE Server & Ole Container?
An Ole server application creates ole Objects that are embedded or linked in ole Containers ex. Ole servers are ms_word & ms_excel. OLE containers provide a place to store, display and manipulate objects that are created by ole server applications. Ex. oracle forms is an example of an ole Container.
27 What is the difference between object embedding & linking in Oracle forms?
In Oracle forms, Embedded objects become part of the form module, and linked objects are references from a form module to a linked source file.
28 What is the difference between boiler plat images and image items?
Boiler plate Images are static images (Either vector or bit map) that you import from the file system or database to use a graphical elements in your form, such as company logos and maps. Image items are special types of interface controls that store and display either vector or bitmap images. Like other items that store values, image items can be either base table items(items that relate directly to database columns) or control items. The definition of an image item is stored as part of the form module FMB and FMX files, but no image file is actually associated with an image item until the item is populate at run time.
29 What is the difference between $$DATE$$ & $$DBDATE$$ $$DBDATE$$ retrieves the current database date $$date$$ retrieves the current operating system date.
30 What is the diff. when Flex mode is mode on and when it is off?
When flex mode is on, reports automatically resizes the parent when the child is resized.
31 What is the diff. when confine mode is on and when it is off?
When confine mode is on, an object cannot be moved outside its parent in the layout.
32 What is the diff. bet. setting up of parameters in reports 2.0 reports 2.5?
LOVs can be attached to parameters in the reports 2.5 parameter form.
33 What is the advantage of the library?
Libraries provide a convenient means of storing client-side program units and sharing them among multiple applications. Once you create a library, you can attach it to any other form, menu, or library modules. When you can call library program units from triggers menu items commands and user named routine, you write in the modules to which you have attach the library. When a library attaches another library, program units in the first library can reference program units in the attached library. Library support dynamic loading-that is library program units are loaded into an application only when needed. This can significantly reduce the run-time memory requirements of applications.
34 What is term?
The term is terminal definition file that describes the terminal form which you are using r20run.
35 What is system.coordination_operation?
It represents the coordination causing event that occur on the master block in master-detail relation.
36 What is synchronize?
It is a terminal screen with the internal state of the form. It updates the screen display to reflect the information that oracle forms has in its internal representation of the screen.
37 What is strip sources generate options?
Removes the source code from the library file and generates a library files that contains only pcode. The resulting file can be used for final deployment, but can not be subsequently edited in the designer. ex. f45gen module=old_lib.pll userid=scott/tiger strip_source YES output_file
38 What is relation between the window and canvas views?
Canvas views are the back ground objects on which you place the interface items (Text items), check boxes, radio groups etc.,) and boilerplate objects (boxes, lines, images etc.,) that operators interact with us they run your form . Each canvas views displayed in a window.
39 What is pop list?
The pop list style list item appears initially as a single field (similar to a text item field). When the operator selects the list icon, a list of available choices appears.
40 What is new_form built-in?
When one form invokes another form by executing new_form oracle form exits the first form and releases its memory before loading the new form calling new form completely replace the first with the second. If there are changes pending in the first form, the operator will be prompted to save them before the new form is loaded.
41 What is lexical reference? How can it be created?
Lexical reference is place_holder for text that can be embedded in a sql statements. A lexical reference can be created using & before the column or parameter name.
42 What is forms_DDL?
Issues dynamic Sql statements at run time, including server side pl/SQl and DDL
43 What is difference between open_form and call_form?
when one form invokes another form by executing open_form the first form remains displayed, and operators can navigate between the forms as desired. when one form invokes another form by executing call_form, the called form is modal with respect to the calling form. That is, any windows that belong to the calling form are disabled, and operators cannot navigate to them until they first exit the called form.
44 What is bind reference and how can it be created?
Bind reference are used to replace the single value in sql, pl/sql statements a bind reference can be created using a (:) before a column or a parameter name.
45 What is an user exit used for?
A way in which to pass control (and possibly arguments ) form Oracle report to another Oracle products of 3 GL and then return control ( and ) back to Oracle reports.
46 What is an OLE?
Object Linking & Embedding provides you with the capability to integrate objects from many Ms-Windows applications into a single compound document creating integrated applications enables you to use the features form .
47 What is an object group?
An object group is a container for a group of objects; you define an object group when you want to package related objects, so that you copy or reference them in other modules.
48 What is an anchoring object & what is its use?
An anchoring object is a print condition object which used to explicitly or implicitly anchor other objects to itself.
49 What is a User_exit?
Calls the user exit named in the user_exit_string. Invokes a 3Gl program by name which has been properly linked into your current oracle forms executable.
50 What is a timer?
Timer is an "internal time clock" that you can programmatically create to perform an action each time the timer expires.
51 What is a Text_io Package?
It allows you to read and write information to a file in the file system.
52 What is a text list?
The text list style list item appears as a rectangular box which displays the fixed number of values. When the text list contains values that can not be displayed, a vertical scroll bar appears, allowing the operator to view and select undisplayed values.
53 What is a property clause?
A property clause is a named object that contains a list of properties and their settings. Once you create a property clause you can base other object on it. An object based on a property can inherit the setting of any property in the clause that makes sense for that object.
54 What is a physical page ? & What is a logical page ?
A physical page is a size of a page. That is output by the printer. The logical page is the size of one page of the actual report as seen in the Previewer.
55 What is a library?
A library is a collection of subprograms including user named procedures, functions and packages.
56 What is a difference between pre-select and pre-query?
Fires during the execute query and count query processing after oracle forms constructs the select statement to be issued, but before the statement is actually issued. The pre-query trigger fires just before oracle forms issues the select statement to the database after the operator as define the example records by entering the query criteria in enter query mode. Pre-query trigger fires before pre-select trigger.
57 What is a combo box?
A combo box style list item combines the features found in list and text item. Unlike the pop list or the text list style list items, the combo box style list item will both display fixed values and accept one operator entered value.
58 What does the term panel refer to with regard to pages?
A panel is the no. of physical pages needed to print one logical page.
59 What are visual attributes?
Visual attributes are the font, color, pattern proprieties that you set for form and menu objects that appear in your application interface.
60 What are three panes that appear in the run time pl/sql interpreter?
1.Source pane. 2. interpreter pane. 3. Navigator pane.
Regards
B RANGARAJAN -
Hi,
I am trying to filter my output from the query based on some conditions but not able to figure out how. May be I am just overlooking at the issue or is it something tricky.
So, I have a query returning 4 rows of output out of which I need to filter the rows. I have created a table from the result of the query that I need to filter to make it simple. So below is my create table script and values that are obtained from my original query.
CREATE TABLE TEMPACCT
SOURCEKEY NUMBER,
FLAG VARCHAR2(1),
ITEMID NUMBER(9) ,
ITEMNAME VARCHAR2(10) ,
ITEMKEY NUMBER(9)
Insert into tempacct values (0, 'N', 100, 'ITEM1' , 9647);
Insert into tempacct values (0, 'N', 200, 'ITEM2' , 9648);
Insert into tempacct values (9648, 'N', 100, 'ITEM3' , 9813);
Insert into tempacct values (9647, 'Y', 100, 'ITEM4' , 9812);
SQL> select * from tempacct;
SOURCEKEY F ITEMID ITEMNAME ITEMKEY
0 N 100 ITEM1 9647
0 N 200 ITEM2 9648
9648 N 100 ITEM3 9813
9647 Y 100 ITEM4 9812
SQL> Tempacct table is the table created from the resultset of my original query.
So from the above output, what I need is 3 rows. The logic to filter out the row is - If any of the row thathas sourcekey that is same as Itemkey in any of the 4 rows and flag is Y then remove the row which have flag =N and only display the one with Falg = Y.
Ok, so, in this case the desired output would be
SOURCEKEY F ITEMID ITEMNAME ITEMKEY
0 N 200 ITEM2 9648
9648 N 100 ITEM3 9813
9647 Y 100 ITEM4 9812So here we compared between the first row and the fourth row, and since the sourcekey in fourth row is same as itemkey in first row and Flag is 'Y' for fourth row, we keep 4th row and remove the first row since the flag is 'N'. (and sourcekey is 0. the row that gets removed will always have sourcekey =0) .
SQL> select * from v$version;
BANNER
Oracle Database 10g Release 10.2.0.4.0 - 64bit Production
PL/SQL Release 10.2.0.4.0 - Production
CORE 10.2.0.4.0 Production
TNS for Linux: Version 10.2.0.4.0 - Production
NLSRTL Version 10.2.0.4.0 - ProductionAppreciate your help.Hi,
ARIZ wrote:
Although the original question is already been answered, I had another small modification to the same question and also seeking some clarification. I do not want to open a new thread just for a similar question.I think you'll get better replies faster if you do start a new thread.
Not counting this one, there have been 13 replies to this thread. Not many people who havn't already been participating in this thread are going to start reading a thread with 13 replies. Those who do are going to waste a lot of time reading about issues that have already been resolved, and the are likely to understand the remaining issues incorrectly.
I have been following the thread from the beginnning, and I'm starting to get confused about what the unresolved issues are.
I believe there are two things you still need:
(1) An explanation of the solution I posted yesterday, involving the analytic COUNT function.
(2) A solution for a new problem involving the same tables
If I got that wrong, start a new thread, asking just what you need to know. Copy any relevant parts (like the CREATE TABLE and INSERT statements) from this thread. You can include a link to this thread, but do your best to make sure people don't have to use it.
I realize that's more work for you, but getting the best results, and getting them quickly, sometimes does require more work.
<h2>(1) An explanation of the solution I posted yesterday, involving the analytic COUNT function.</h2>
ARIZ wrote:
Hi Frank,
Just out of curiosity, I was trying to understand the Count analytical function that you have used in the solution.
COUNT ( CASE
WHEN ac.flag = 'Y'
THEN 1
END
) OVER ( PARTITION BY CASE
WHEN sourcekey = 0
THEN acctkey
ELSE sourcekey
END
) AS y_cntSo what I am thinking is, this would first partition the row with acctkey ( where sourcekey =0) and sourcekey and then within that partition, it will check whether ac.flag = Y or not, if it is 'Y' then it would return count as 1 else 0. Am I correct? In the mean time I am also reading the tutorials on Count() analytical query. I'm not sure I understand your explanation.
This is not partitioning first by x, and then by y. There is only one expression in the PARTITION BY clause. Most often, a PARTITION BY clause refers to some column in the table, for example:
SELECT ename
, job
, sal
, AVG (sal) OVER (PARTITION BY job) AS avg_sal_for_job
FROM scott.emp;This divides the result set into mutually exclusive parts; there will be as many such parts as there are distinct values for the PARTITION BY column. In the simple query above, if there happen to be 5 different values for job, you will get 5 independent averages.
In your problem, there is no one column that defines a partition. That is, these two rows belong to the same partition:
. SOURCEKEY F ACCTKEY
0 N 9647
9647 Y 9812even though none of the 3 columns are the same. We could create a view that had a single column, telling to which partition each row belonged, like this:
. SOURCEKEY F ACCTKEY PART_NUM
0 N 9648 9648
0 N 9647 9647
9648 N 9813 9648
9647 Y 9812 9647where part_num is the result of a CASE expression:
CASE
WHEN sourcekey = 0
THEN acctkey
ELSE sourcekey
ENDWe could then use that new column, part_num, in a (very simple) PARTITION BY clause. But there is no need to create a view, even an in-line view, for that: we can (and I did) use the CASE expression directly in a (not so simple) PARTITION BY clause.
Why did I use COUNT? The important thing about each partition is whether or not it includes any rows with flag='Y'. I don;t know of any function that directly answers that question. There are lots of ways to get the correct answer, but I think the one that corresponds most closely to the question we really want to ask:
"Do any rows have flag='Y'?" is
"How many rows have flag='Y'?"
The analytic function COUNT (x) returns a number (possibly 0) of rows in the partition where x is not NULL. So, as the argument to COUNT, I used
CASE
WHEN ac.flag = 'Y'
THEN 1
-- ELSE NULL -- I did not explicitly say this, but it is the default
ENDwhich returns either
(a) the literal number 1 or
(b) NULL
Instead of the literanl number 1, I could have used any literal or expression, of any data type, that is not NULL). all that matters is we produce something non-NULL for COUNT to count.
<h2>(2) A solution for a new problem involving the same tables</h2>
Also, I was trying to modify this query to fit my other similar requirement where I would need following output
Original output:
SOURCEKEY F ACCTKEY
0 N 9648
0 N 9647
9648 N 9813
9647 Y 9812
So, the query should be smart enough to return only the last two rows where sourcekey >0 which is
SOURCEKEY F ACCTKEY
9648 N 9813
9647 Y 9812
And In case there are only first two 2 rows in the table then , it should return only those two row and not check for sourcekey > 0 which would be .
SOURCEKEY F ACCTKEY
0 N 9648
0 N 9647 Is it something that I should be using analytical function to solve this requirement. I am trying to accomplish this new requirement.If I understand this problem correctly, it does indeed involve mutually exclusive divisions, but in this problem, the divisions correspond more closely to a single column in the table. We want to divide the table into two mutually exclusive groups:
(A) rows where soucekey > 0, and
(B) rows where sourcekey = 0
We could do that with a CASE expression, but there happens to be a built-in function that works very nicely.
SIGN (sourcekey) returns
(A) 1 if sourcekey > 0, and
(B) 0 if sourcekey = 0
But what do we want to do with those divisions? We want to display rows only from the "best" of those divisions, where division (A) is coinsidered "better" than division (B). That is, if there are any rows in division (A), then we want to display only rows in division (A), but if there are no rows in division (A), then (and only then) we want to display rows in divison (B).
This is an example of a Top-N Query , where we want to display N items from the top of an ordered list. A typical top-N query uses an analytic function (either ROW_NUMBER, RANK or DENSE_RANK, depending on how we want to handle ties) to assign numbers to each row (lower numbers for the "better" rows), and then uses "WHERE f <= n" to display only the n "best" ones. (A special case, though a very common one, is where N=1, that is, we're only interested in the row (or rows, if there happens to be a tie) with the "best" value. In this case, most people find it cleare to say "WHERE f = 1" ratehr than "WHERE f <= 1". Your problem is an exmple ot that special case.)
SELECT sourcekey
, flag
, acctkey
FROM (
SELECT ac.sourcekey
, NVL (ac.flag, 'N') AS flag
, ac.acctkey
, DENSE_RANK () OVER (ORDER BY SIGN (sourcekey) DESC) AS division_num
FROM itemtable i
, finance f
, acct ac
WHERE i.itemtableid1 = f.parentid1
AND i.itemtableid2 = f.parentid2
AND f.financekey = ac.financekey
AND i.parenttableid = 19063
WHERE division_num = 1
;Notice I talked about "mutually exclusiive *divisions* " above, not "mutually exclusive *partitions* ".
There is no PARTITION BY in the analytic clause above. PARTITION BY means we want a separate, independent caluclation for each partition. Here, we want one single numbering for the entire result set.
We want all rows that tie for the "best" to be numbered 1, so we have to use DENSE_RANK (or RANK) rather than ROW_NUMBER. -
Serial table scan with direct path read compared to db file scattered read
Hi,
The environment
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit
8K block size
db_file_multiblock_read_count is 128
show sga
Total System Global Area 1.6702E+10 bytes
Fixed Size 2219952 bytes
Variable Size 7918846032 bytes
Database Buffers 8724152320 bytes
Redo Buffers 57090048 bytes
16GB of SGA with 8GB of db buffer cache.
-- database is built on Solid State Disks
-- SQL trace and wait events
DBMS_MONITOR.SESSION_TRACE_ENABLE ( waits=>true )
-- The underlying table is called tdash. It has 1.7 Million rows based on data in all_objects. NO index
TABLE_NAME Rows Table Size/MB Used/MB Free/MB
TDASH 1,729,204 15,242 15,186 56
TABLE_NAME Allocated blocks Empty blocks Average space/KB Free list blocks
TDASH 1,943,823 7,153 805 0
Objectives
To show that when serial scans are performed on database built on Solid State Disks (SSD) compared to Magnetic disks (HDD), the performance gain is far less compared to random reads with index scans on SSD compared to HDD
Approach
We want to read the first 100 rows of tdash table randomly into buffer, taking account of wait events and wait times generated. The idea is that on SSD the wait times will be better compared to HDD but not that much given the serial nature of table scans.
The code used
ALTER SESSION SET TRACEFILE_IDENTIFIER = 'test_with_tdash_ssdtester_noindex';
DECLARE
type array is table of tdash%ROWTYPE index by binary_integer;
l_data array;
l_rec tdash%rowtype;
BEGIN
SELECT
a.*
,RPAD('*',4000,'*') AS PADDING1
,RPAD('*',4000,'*') AS PADDING2
BULK COLLECT INTO
l_data
FROM ALL_OBJECTS a;
DBMS_MONITOR.SESSION_TRACE_ENABLE ( waits=>true );
FOR rs IN 1 .. 100
LOOP
BEGIN
SELECT * INTO l_rec FROM tdash WHERE object_id = l_data(rs).object_id;
EXCEPTION
WHEN NO_DATA_FOUND THEN NULL;
END;
END LOOP;
END;
/Server is rebooted prior to any tests
Whern run as default, the optimizer (although some attribute this to the execution engine) chooses direct path read into PGA in preference to db file scattered read.
With this choice it takes 6,520 seconds to complete the query. The results are shown below
SQL ID: 78kxqdhk1ubvq
Plan Hash: 1148949653
SELECT *
FROM
TDASH WHERE OBJECT_ID = :B1
call count cpu elapsed disk query current rows
Parse 1 0.01 0.00 2 47 0 0
Execute 100 0.00 0.00 1 51 0 0
Fetch 100 10.88 6519.89 194142802 194831012 0 100
total 201 10.90 6519.90 194142805 194831110 0 100
Misses in library cache during parse: 1
Optimizer mode: ALL_ROWS
Parsing user id: 96 (SSDTESTER) (recursive depth: 1)
Rows Row Source Operation
1 TABLE ACCESS FULL TDASH (cr=1948310 pr=1941430 pw=0 time=0 us cost=526908 size=8091 card=1)
Rows Execution Plan
0 SELECT STATEMENT MODE: ALL_ROWS
1 TABLE ACCESS MODE: ANALYZED (FULL) OF 'TDASH' (TABLE)
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
Disk file operations I/O 3 0.00 0.00
db file sequential read 2 0.00 0.00
direct path read 1517504 0.05 6199.93
asynch descriptor resize 196 0.00 0.00
DECLARE
type array is table of tdash%ROWTYPE index by binary_integer;
l_data array;
l_rec tdash%rowtype;
BEGIN
SELECT
a.*
,RPAD('*',4000,'*') AS PADDING1
,RPAD('*',4000,'*') AS PADDING2
BULK COLLECT INTO
l_data
FROM ALL_OBJECTS a;
DBMS_MONITOR.SESSION_TRACE_ENABLE ( waits=>true );
FOR rs IN 1 .. 100
LOOP
BEGIN
SELECT * INTO l_rec FROM tdash WHERE object_id = l_data(rs).object_id;
EXCEPTION
WHEN NO_DATA_FOUND THEN NULL;
END;
END LOOP;
END;
call count cpu elapsed disk query current rows
Parse 0 0.00 0.00 0 0 0 0
Execute 1 3.84 4.03 320 48666 0 1
Fetch 0 0.00 0.00 0 0 0 0
total 1 3.84 4.03 320 48666 0 1
Misses in library cache during parse: 0
Misses in library cache during execute: 1
Optimizer mode: ALL_ROWS
Parsing user id: 96 (SSDTESTER)
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
SQL*Net message to client 1 0.00 0.00
SQL*Net message from client 1 0.00 0.00
SQL ID: 9babjv8yq8ru3
Plan Hash: 0
BEGIN DBMS_OUTPUT.GET_LINES(:LINES, :NUMLINES); END;
call count cpu elapsed disk query current rows
Parse 1 0.00 0.00 0 0 0 0
Execute 1 0.00 0.00 0 0 0 1
Fetch 0 0.00 0.00 0 0 0 0
total 2 0.00 0.00 0 0 0 1
Misses in library cache during parse: 0
Optimizer mode: ALL_ROWS
Parsing user id: 96 (SSDTESTER)
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
SQL*Net message to client 1 0.00 0.00
SQL*Net message from client 1 0.00 0.00
OVERALL TOTALS FOR ALL NON-RECURSIVE STATEMENTS
call count cpu elapsed disk query current rows
Parse 1 0.00 0.00 0 0 0 0
Execute 2 3.84 4.03 320 48666 0 2
Fetch 0 0.00 0.00 0 0 0 0
total 3 3.84 4.03 320 48666 0 2
Misses in library cache during parse: 0
Misses in library cache during execute: 1
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
SQL*Net message to client 2 0.00 0.00
SQL*Net message from client 2 0.00 0.00
log file sync 1 0.00 0.00
OVERALL TOTALS FOR ALL RECURSIVE STATEMENTS
call count cpu elapsed disk query current rows
Parse 9 0.01 0.00 2 47 0 0
Execute 129 0.01 0.00 1 52 2 1
Fetch 140 10.88 6519.89 194142805 194831110 0 130
total 278 10.91 6519.91 194142808 194831209 2 131
Misses in library cache during parse: 9
Misses in library cache during execute: 8
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
db file sequential read 5 0.00 0.00
Disk file operations I/O 3 0.00 0.00
direct path read 1517504 0.05 6199.93
asynch descriptor resize 196 0.00 0.00
102 user SQL statements in session.
29 internal SQL statements in session.
131 SQL statements in session.
1 statement EXPLAINed in this session.
Trace file: mydb_ora_16394_test_with_tdash_ssdtester_noindex.trc
Trace file compatibility: 11.1.0.7
Sort options: default
1 session in tracefile.
102 user SQL statements in trace file.
29 internal SQL statements in trace file.
131 SQL statements in trace file.
11 unique SQL statements in trace file.
1 SQL statements EXPLAINed using schema:
ssdtester.plan_table
Schema was specified.
Table was created.
Table was dropped.
1531657 lines in trace file.
6520 elapsed seconds in trace file.I then force the query not to use direct path read by invoking
ALTER SESSION SET EVENTS '10949 trace name context forever, level 1' -- No Direct path read ;In this case the optimizer uses db file scattered read predominantly and the query takes 4,299 seconds to finish which is around 34% faster than using direct path read (default).
The report is shown below
SQL ID: 78kxqdhk1ubvq
Plan Hash: 1148949653
SELECT *
FROM
TDASH WHERE OBJECT_ID = :B1
call count cpu elapsed disk query current rows
Parse 1 0.00 0.00 2 47 0 0
Execute 100 0.00 0.00 2 51 0 0
Fetch 100 143.44 4298.87 110348670 194490912 0 100
total 201 143.45 4298.88 110348674 194491010 0 100
Misses in library cache during parse: 1
Optimizer mode: ALL_ROWS
Parsing user id: 96 (SSDTESTER) (recursive depth: 1)
Rows Row Source Operation
1 TABLE ACCESS FULL TDASH (cr=1944909 pr=1941430 pw=0 time=0 us cost=526908 size=8091 card=1)
Rows Execution Plan
0 SELECT STATEMENT MODE: ALL_ROWS
1 TABLE ACCESS MODE: ANALYZED (FULL) OF 'TDASH' (TABLE)
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
Disk file operations I/O 3 0.00 0.00
db file sequential read 129759 0.01 17.50
db file scattered read 1218651 0.05 3770.02
latch: object queue header operation 2 0.00 0.00
DECLARE
type array is table of tdash%ROWTYPE index by binary_integer;
l_data array;
l_rec tdash%rowtype;
BEGIN
SELECT
a.*
,RPAD('*',4000,'*') AS PADDING1
,RPAD('*',4000,'*') AS PADDING2
BULK COLLECT INTO
l_data
FROM ALL_OBJECTS a;
DBMS_MONITOR.SESSION_TRACE_ENABLE ( waits=>true );
FOR rs IN 1 .. 100
LOOP
BEGIN
SELECT * INTO l_rec FROM tdash WHERE object_id = l_data(rs).object_id;
EXCEPTION
WHEN NO_DATA_FOUND THEN NULL;
END;
END LOOP;
END;
call count cpu elapsed disk query current rows
Parse 0 0.00 0.00 0 0 0 0
Execute 1 3.92 4.07 319 48625 0 1
Fetch 0 0.00 0.00 0 0 0 0
total 1 3.92 4.07 319 48625 0 1
Misses in library cache during parse: 0
Misses in library cache during execute: 1
Optimizer mode: ALL_ROWS
Parsing user id: 96 (SSDTESTER)
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
SQL*Net message to client 1 0.00 0.00
SQL*Net message from client 1 0.00 0.00
SQL ID: 9babjv8yq8ru3
Plan Hash: 0
BEGIN DBMS_OUTPUT.GET_LINES(:LINES, :NUMLINES); END;
call count cpu elapsed disk query current rows
Parse 1 0.00 0.00 0 0 0 0
Execute 1 0.00 0.00 0 0 0 1
Fetch 0 0.00 0.00 0 0 0 0
total 2 0.00 0.00 0 0 0 1
Misses in library cache during parse: 0
Optimizer mode: ALL_ROWS
Parsing user id: 96 (SSDTESTER)
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
SQL*Net message to client 1 0.00 0.00
SQL*Net message from client 1 0.00 0.00
OVERALL TOTALS FOR ALL NON-RECURSIVE STATEMENTS
call count cpu elapsed disk query current rows
Parse 1 0.00 0.00 0 0 0 0
Execute 2 3.92 4.07 319 48625 0 2
Fetch 0 0.00 0.00 0 0 0 0
total 3 3.92 4.07 319 48625 0 2
Misses in library cache during parse: 0
Misses in library cache during execute: 1
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
SQL*Net message to client 2 0.00 0.00
SQL*Net message from client 2 0.00 0.00
log file sync 1 0.00 0.00
OVERALL TOTALS FOR ALL RECURSIVE STATEMENTS
call count cpu elapsed disk query current rows
Parse 9 0.01 0.00 2 47 0 0
Execute 129 0.00 0.00 2 52 2 1
Fetch 140 143.44 4298.87 110348674 194491010 0 130
total 278 143.46 4298.88 110348678 194491109 2 131
Misses in library cache during parse: 9
Misses in library cache during execute: 8
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
db file sequential read 129763 0.01 17.50
Disk file operations I/O 3 0.00 0.00
db file scattered read 1218651 0.05 3770.02
latch: object queue header operation 2 0.00 0.00
102 user SQL statements in session.
29 internal SQL statements in session.
131 SQL statements in session.
1 statement EXPLAINed in this session.
Trace file: mydb_ora_26796_test_with_tdash_ssdtester_noindex_NDPR.trc
Trace file compatibility: 11.1.0.7
Sort options: default
1 session in tracefile.
102 user SQL statements in trace file.
29 internal SQL statements in trace file.
131 SQL statements in trace file.
11 unique SQL statements in trace file.
1 SQL statements EXPLAINed using schema:
ssdtester.plan_table
Schema was specified.
Table was created.
Table was dropped.
1357958 lines in trace file.
4299 elapsed seconds in trace file.I note that there are 1,517,504 waits with direct path read with total time of nearly 6,200 seconds. In comparison with no direct path read, there are 1,218,651 db file scattered read waits with total wait time of 3,770 seconds. My understanding is that direct path read can use single or multi-block read into the PGA. However db file scattered reads do multi-block read into multiple discontinuous SGA buffers. So it is possible given the higher number of direct path waits that the optimizer cannot do multi-block reads (contigious buffers within PGA) and hence has to revert to single blocks reads which results in more calls and more waits?.
Appreciate any advise and apologies for being long winded.
Thanks,
MichHi Charles,
I am doing your tests for t1 table using my server.
Just to clarify my environment is:
I did the whole of this test on my server. My server has I7-980 HEX core processor with 24GB of RAM and 1 TB of HDD SATA II for test/scratch backup and archive. The operating system is RHES 5.2 64-bit installed on a 120GB OCZ Vertex 3 Series SATA III 2.5-inch Solid State Drive.
Oracle version installed was 11g Enterprise Edition Release 11.2.0.1.0 -64bit. The binaries were created on HDD. Oracle itself was configured with 16GB of SGA, of which 7.5GB was allocated to Variable Size and 8GB to Database Buffers.
For Oracle tablespaces including SYS, SYSTEM, SYSAUX, TEMPORARY, UNDO and redo logs, I used file systems on 240GB OCZ Vertex 3 Series SATA III 2.5-inch Solid State Drive. With 4K Random Read at 53,500 IOPS and 4K Random Write at 56,000 IOPS (manufacturer’s figures), this drive is probably one of the fastest commodity SSDs using NAND flash memory with Multi-Level Cell (MLC). Now my T1 table created as per your script and has the following rows and blocks (8k block size)
SELECT
NUM_ROWS,
BLOCKS
FROM
USER_TABLES
WHERE
TABLE_NAME='T1';
NUM_ROWS BLOCKS
12000000 178952which is pretty identical to yours.
Then I run the query as brelow
set timing on
ALTER SESSION SET TRACEFILE_IDENTIFIER = 'test_bed_T1';
ALTER SESSION SET EVENTS '10046 TRACE NAME CONTEXT FOREVER, LEVEL 8';
SELECT
COUNT(*)
FROM
T1
WHERE
RN=1;
which gives
COUNT(*)
60000
Elapsed: 00:00:05.29
tkprof output shows
call count cpu elapsed disk query current rows
Parse 1 0.00 0.00 0 0 0 0
Execute 1 0.00 0.00 0 0 0 0
Fetch 2 0.02 5.28 178292 178299 0 1
total 4 0.02 5.28 178292 178299 0 1
Compared to yours:
Fetch 2 0.60 4.10 178493 178498 0 1
It appears to me that my CPU utilisation is by order of magnitude better but my elapsed time is worse!
Now the way I see it elapsed time = CPU time + wait time. Further down I have
Rows Row Source Operation
1 SORT AGGREGATE (cr=178299 pr=178292 pw=0 time=0 us)
60000 TABLE ACCESS FULL T1 (cr=178299 pr=178292 pw=0 time=42216 us cost=48697 size=240000 card=60000)
Rows Execution Plan
0 SELECT STATEMENT MODE: ALL_ROWS
1 SORT (AGGREGATE)
60000 TABLE ACCESS MODE: ANALYZED (FULL) OF 'T1' (TABLE)
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
SQL*Net message to client 3 0.00 0.00
SQL*Net message from client 3 0.00 0.00
Disk file operations I/O 3 0.00 0.00
direct path read 1405 0.00 4.68
Your direct path reads are
direct path read 1404 0.01 3.40Which indicates to me you have faster disks compared to mine, whereas it sounds like my CPU is faster than yours.
With db file scattered read I get
Elapsed: 00:00:06.95
call count cpu elapsed disk query current rows
Parse 1 0.00 0.00 0 0 0 0
Execute 1 0.00 0.00 0 0 0 0
Fetch 2 1.22 6.93 178293 178315 0 1
total 4 1.22 6.94 178293 178315 0 1
Rows Row Source Operation
1 SORT AGGREGATE (cr=178315 pr=178293 pw=0 time=0 us)
60000 TABLE ACCESS FULL T1 (cr=178315 pr=178293 pw=0 time=41832 us cost=48697 size=240000 card=60000)
Rows Execution Plan
0 SELECT STATEMENT MODE: ALL_ROWS
1 SORT (AGGREGATE)
60000 TABLE ACCESS MODE: ANALYZED (FULL) OF 'T1' (TABLE)
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
SQL*Net message to client 2 0.00 0.00
Disk file operations I/O 3 0.00 0.00
db file sequential read 1 0.00 0.00
db file scattered read 1414 0.00 5.36
SQL*Net message from client 2 0.00 0.00
compared to your
db file scattered read 1415 0.00 4.16On the face of it with this test mine shows 21% improvement with direct path read compared to db scattered file read. So now I can go back to re-visit my original test results:
First default with direct path read
call count cpu elapsed disk query current rows
Parse 1 0.01 0.00 2 47 0 0
Execute 100 0.00 0.00 1 51 0 0
Fetch 100 10.88 6519.89 194142802 194831012 0 100
total 201 10.90 6519.90 194142805 194831110 0 100
CPU ~ 11 sec, elapsed ~ 6520 sec
wait stats
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
direct path read 1517504 0.05 6199.93
roughly 0.004 sec for each I/ONow with db scattered file read I get
call count cpu elapsed disk query current rows
Parse 1 0.00 0.00 2 47 0 0
Execute 100 0.00 0.00 2 51 0 0
Fetch 100 143.44 4298.87 110348670 194490912 0 100
total 201 143.45 4298.88 110348674 194491010 0 100
CPU ~ 143 sec, elapsed ~ 4299 sec
and waits:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
db file sequential read 129759 0.01 17.50
db file scattered read 1218651 0.05 3770.02
roughly 17.5/129759 = .00013 sec for single block I/O and 3770.02/1218651 = .0030 for multi-block I/ONow my theory is that the improvements comes from the large buffer cache (8320MB) inducing it to do some read aheads (async pre-fetch). Read aheads are like quasi logical I/Os and they will be cheaper compared to physical I/O. When there is large buffer cache and read aheads can be done then using buffer cache is a better choice than PGA?
Regards,
Mich -
A lot of messages "direct path write temp" and "direct path read temp"
Hello, all
Please, understand me, what is going on in my system (DB: Oracle database 11.2.0.3, OS: Windows 2008 R2).
In AWR report (1 hour) I see next:
Foreground Wait Events
Avg
%Time Total Wait wait Waits % DB
Event Waits -outs Time (s) (ms) /txn time
direct path write temp 132,627 0 1,056 8 0.8 21.7
direct path read temp 308,969 0 565 2 2.0 11.6
log file sync 19,228 0 241 13 0.1 5.0
direct path write 17,698 0 135 8 0.1 2.8
db file sequential read 21,149 0 94 4 0.1 1.9
SQL*Net message from dblin 59 0 5 86 0.0 .1
Segments by Direct Physical Reads DB/Inst: SGRE/sgre Snaps: 1039-1040
-> Total Direct Physical Reads: 392,273
-> Captured Segments account for 94.7% of Total
Tablespace Subobject Obj. Direct
Owner Name Object Name Name Type Reads %Total
** MISSING TEMP ** TRANSIENT: 437734 MISSING ** UNDEF 38,290 9.76
DBSNMP TEMP MGMT_TEMPT_SQL TABLE 38,242 9.75
** MISSING TEMP ** TRANSIENT: 438784 MISSING ** UNDEF 37,790 9.63
** MISSING TEMP ** TRANSIENT: 437312 MISSING ** UNDEF 37,661 9.60
** MISSING TEMP ** TRANSIENT: 439257 MISSING ** UNDEF 37,477 9.55Some selects:
SELECT S.sid,
T.blocks * TBS.block_size / 1024 / 1024 mb_used, T.tablespace, T.SEGTYPE
FROM v$sort_usage T, v$session S, v$sqlarea Q, dba_tablespaces TBS
WHERE T.session_addr = S.saddr
AND T.sqladdr = Q.address (+)
AND T.tablespace = TBS.tablespace_name
AND S.sid = 732
ORDER BY S.username, S.sid;
SID MB_USED TABLESPACE SEGTYPE
732 2 TEMP LOB_DATA
732 1 TEMP INDEX
732 1 TEMP DATA
732 1 TEMP INDEX
732 1 TEMP DATA
732 1 TEMP INDEX
732 1 TEMP DATA
732 1 TEMP INDEX
732 1 TEMP INDEX
732 1 TEMP DATA
732 1 TEMP INDEX
732 1 TEMP INDEX
732 1 TEMP DATA
732 1 TEMP INDEX
732 1 TEMP INDEX
732 1 TEMP DATA
732 1 TEMP INDEX
732 1 TEMP INDEX
732 1 TEMP DATA
732 1 TEMP INDEX
732 1 TEMP INDEX
732 1 TEMP DATA
732 1 TEMP INDEX
732 1 TEMP INDEX
732 1 TEMP DATA
732 1 TEMP INDEX
732 1 TEMP INDEX
732 1 TEMP DATA
732 1 TEMP INDEX
732 1 TEMP LOB_INDEX
select st.sid, sn.name, st.VALUE
from V$statname sn, v$sesstat st
where st.STATISTIC# = sn.STATISTIC#
and (sn.name like 'sorts%')
and st.sid in (select sid from v$session_wait where event like '%direct path write temp%')
order by st.sid
SID NAME VALUE
732 sorts (memory) 591408
732 sorts (rows) 102126
732 sorts (disk) 0Why I do not see any disk sorts? If TEMP is used for no sort operations, then for which operations?
How I can see that? How can I decrease direct path write temp without tuning SQL?
Additional information:
PGA_AGGREGATE_TARGET is set to big value - 6GB (3GB enough due to advisory recommendation)
Please, help.
Regards, user12103911.user12103911 wrote:
SELECT optimal_count, round(optimal_count*100/total, 2) optimal_perc,
onepass_count, round(onepass_count*100/total, 2) onepass_perc,
multipass_count, round(multipass_count*100/total, 2) multipass_perc
FROM
(SELECT decode(sum(total_executions), 0, 1, sum(total_executions)) total,
sum(OPTIMAL_EXECUTIONS) optimal_count,
sum(ONEPASS_EXECUTIONS) onepass_count,
sum(MULTIPASSES_EXECUTIONS) multipass_count
FROM v$sql_workarea_histogram);
OPTIMAL_COUNT OPTIMAL_PERC ONEPASS_COUNT ONEPASS_PERC MULTIPASS_COUNT MULTIPASS_PERC
13150685 100 0 0 0 0No n-pass executions.That's a pretty convincing display - given that your AWR manages to NAME an object that is in the TEMP tablespace, an obvious point to follow up is global temporary tables. If you have any declared as "on commit preserve" (duration = 'SYS$SESSION') then you could have code which does "insert /*+ append */ into gtt", and if you then query this in parallel (or - since you're on 11.2.0.3 - the data volume is large enough) Oracle could choose to do direct path writes to load the GTT and direct path reads to read it back.
Regards
Jonathan Lewis -
Wait events 'direct path write' and 'direct path read'
Hi,
We have a query which is taking more that 2 min. It's a 9.2.0.7 database. We took the trace/tkprof of the query,and identified that there are so manay 'direct path write' and 'direct path read' wait events in the trace file.
WAIT #3: nam='direct path write' ela= 5 p1=201 p2=70710 p3=15
WAIT #3: nam='direct path read' ela= 170 p1=201 p2=71719 p3=15
In the above, "p1=201" is a file_id, but we could not find any data file, temp file, control file with that id# 201.
Can you please let us know what's "p1=201" here, how to identify the file which is causing the issue.
Thanks
SravanWhat does:
show parameter db_filesreturn? My guess, is that it returns 200.
The direct file read and direct file write events are reads and writes to TEMP tablespace. In those wait events, the file# is reported as db_files+temp file id. So, 201 means temp file #1.
Now, as to your actual performance problem.
Without seeing the SQL and the corresponding execution plan, it's impossible to be sure. However, the most common causes of temp writes are sort operations and group by operations.
If you decide to post your SQL and execution plan, please be sure to make it readable by formatting it. Information on how to do so can be found here.
Hope that helps,
-Mark
Edited by: mbobak on May 1, 2011 1:50 AM -
Hi All,
DB version is 10.2.0.4
An insert statement is running for almost 14 hours now. The wait event shows direct path read temp
SID EVENT WAIT_TIME SECONDS_IN_WAIT P1 P2
1264 direct path read temp -1 0 524 64626Read about this event, which says it might happen due to Parallel full table scan not using the index. But that is not happening here..
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
| 0 | INSERT STATEMENT | | 1 | 512 | 941 (1)| 00:00:12 |
| 1 | COUNT | | | | | |
|* 2 | FILTER | | | | | |
| 3 | NESTED LOOPS | | 1 | 512 | 941 (1)| 00:00:12 |
| 4 | NESTED LOOPS | | 1 | 506 | 940 (1)| 00:00:12 |
| 5 | NESTED LOOPS | | 1 | 493 | 938 (1)| 00:00:12 |
| 6 | NESTED LOOPS | | 1 | 478 | 937 (1)| 00:00:12 |
| 7 | NESTED LOOPS | | 1 | 439 | 936 (1)| 00:00:12 |
| 8 | NESTED LOOPS | | 1 | 420 | 934 (1)| 00:00:12 |
| 9 | NESTED LOOPS | | 1 | 382 | 932 (1)| 00:00:12 |
| 10 | NESTED LOOPS | | 1 | 377 | 931 (1)| 00:00:12 |
| 11 | NESTED LOOPS | | 1 | 295 | 929 (1)| 00:00:12 |
| 12 | NESTED LOOPS | | 1 | 280 | 927 (1)| 00:00:12 |
| 13 | NESTED LOOPS | | 1 | 273 | 927 (1)| 00:00:12 |
| 14 | NESTED LOOPS | | 1 | 247 | 925 (1)| 00:00:12 |
| 15 | NESTED LOOPS | | 1 | 239 | 924 (1)| 00:00:12 |
| 16 | NESTED LOOPS | | 1 | 212 | 922 (1)| 00:00:12 |
| 17 | NESTED LOOPS | | 1 | 205 | 921 (1)| 00:00:12 |
| 18 | NESTED LOOPS | | 1 | 184 | 156 (1)| 00:00:02 |
| 19 | NESTED LOOPS | | 1 | 109 | 154 (1)| 00:00:02 |
| 20 | NESTED LOOPS | | 1 | 93 | 153 (1)| 00:00:02 |
|* 21 | HASH JOIN | | 4 | 284 | 145 (1)| 00:00:02 |
|* 22 | TABLE ACCESS BY INDEX ROWID | GL_JE_LINES | 65 | 2730 | 130 (0)| 00:00:02 |
| 23 | NESTED LOOPS | | 75 | 4500 | 140 (0)| 00:00:02 |
| 24 | MERGE JOIN CARTESIAN | | 1 | 18 | 10 (0)| 00:00:01 |
| 25 | TABLE ACCESS FULL | FND_PRODUCT_GROUPS | 1 | 2 | 2 (0)| 00:00:01 |
| 26 | BUFFER SORT | | 1 | 16 | 8 (0)| 00:00:01 |
|* 27 | TABLE ACCESS BY INDEX ROWID| GL_CODE_COMBINATIONS | 1 | 16 | 8 (0)| 00:00:01 |
|* 28 | INDEX RANGE SCAN | JSW_GL_CODE_COMB_SEG_IDX | 10 | | 2 (0)| 00:00:01 |
|* 29 | INDEX RANGE SCAN | GL_JE_LINES_N1 | 933 | | 6 (0)| 00:00:01 |
|* 30 | TABLE ACCESS FULL | GL_PERIODS | 5 | 55 | 4 (0)| 00:00:01 |
|* 31 | TABLE ACCESS BY INDEX ROWID | GL_JE_HEADERS | 1 | 22 | 2 (0)| 00:00:01 |
|* 32 | INDEX UNIQUE SCAN | GL_JE_HEADERS_U1 | 1 | | 1 (0)| 00:00:01 |
| 33 | TABLE ACCESS BY INDEX ROWID | GL_CODE_COMBINATIONS | 1 | 16 | 1 (0)| 00:00:01 |
|* 34 | INDEX UNIQUE SCAN | GL_CODE_COMBINATIONS_U1 | 1 | | 0 (0)| 00:00:01 |
|* 35 | TABLE ACCESS BY INDEX ROWID | GL_JE_BATCHES | 1 | 75 | 2 (0)| 00:00:01 |
|* 36 | INDEX UNIQUE SCAN | GL_JE_BATCHES_U1 | 1 | | 1 (0)| 00:00:01 |
|* 37 | TABLE ACCESS BY INDEX ROWID | MTL_TRANSACTION_ACCOUNTS | 1 | 21 | 765 (0)| 00:00:10 |
|* 38 | INDEX RANGE SCAN | MTL_TRANSACTION_ACCOUNTS_N3 | 4021 | | 28 (0)| 00:00:01 |
|* 39 | TABLE ACCESS BY INDEX ROWID | HR_ALL_ORGANIZATION_UNITS | 1 | 7 | 1 (0)| 00:00:01 |
|* 40 | INDEX UNIQUE SCAN | HR_ORGANIZATION_UNITS_PK | 1 | | 0 (0)| 00:00:01 |
|* 41 | TABLE ACCESS BY INDEX ROWID | HR_ORGANIZATION_INFORMATION | 1 | 27 | 2 (0)| 00:00:01 |
|* 42 | INDEX RANGE SCAN | HR_ORGANIZATION_INFORMATIO_FK2 | 1 | | 1 (0)| 00:00:01 |
| 43 | TABLE ACCESS BY INDEX ROWID | MTL_PARAMETERS | 1 | 8 | 1 (0)| 00:00:01 |
|* 44 | INDEX UNIQUE SCAN | MTL_PARAMETERS_U1 | 1 | | 0 (0)| 00:00:01 |
|* 45 | TABLE ACCESS BY INDEX ROWID | HR_ORGANIZATION_INFORMATION | 1 | 26 | 2 (0)| 00:00:01 |
|* 46 | INDEX RANGE SCAN | HR_ORGANIZATION_INFORMATIO_FK2 | 1 | | 1 (0)| 00:00:01 |
|* 47 | INDEX UNIQUE SCAN | HR_ALL_ORGANIZATION_UNTS_TL_PK | 1 | 7 | 0 (0)| 00:00:01 |
|* 48 | TABLE ACCESS BY INDEX ROWID | MTL_MATERIAL_TRANSACTIONS | 1 | 15 | 2 (0)| 00:00:01 |
|* 49 | INDEX UNIQUE SCAN | MTL_MATERIAL_TRANSACTIONS_U1 | 1 | | 1 (0)| 00:00:01 |
| 50 | TABLE ACCESS BY INDEX ROWID | MTL_SYSTEM_ITEMS_B | 1 | 82 | 2 (0)| 00:00:01 |
|* 51 | INDEX UNIQUE SCAN | MTL_SYSTEM_ITEMS_B_U1 | 1 | | 1 (0)| 00:00:01 |
|* 52 | INDEX FULL SCAN | GL_SETS_OF_BOOKS_U2 | 1 | 5 | 1 (0)| 00:00:01 |
|* 53 | TABLE ACCESS BY INDEX ROWID | RCV_TRANSACTIONS | 1 | 38 | 2 (0)| 00:00:01 |
|* 54 | INDEX UNIQUE SCAN | RCV_TRANSACTIONS_U1 | 1 | | 1 (0)| 00:00:01 |
|* 55 | TABLE ACCESS BY INDEX ROWID | PO_HEADERS_ALL | 1 | 19 | 2 (0)| 00:00:01 |
|* 56 | INDEX UNIQUE SCAN | PO_HEADERS_U1 | 1 | | 1 (0)| 00:00:01 |
| 57 | TABLE ACCESS BY INDEX ROWID | PO_VENDORS | 1 | 39 | 1 (0)| 00:00:01 |
|* 58 | INDEX UNIQUE SCAN | PO_VENDORS_U1 | 1 | | 0 (0)| 00:00:01 |
| 59 | TABLE ACCESS BY INDEX ROWID | PO_VENDOR_SITES_ALL | 1 | 15 | 1 (0)| 00:00:01 |
|* 60 | INDEX UNIQUE SCAN | PO_VENDOR_SITES_U1 | 1 | | 0 (0)| 00:00:01 |
| 61 | TABLE ACCESS BY INDEX ROWID | RCV_SHIPMENT_HEADERS | 1 | 13 | 2 (0)| 00:00:01 |
|* 62 | INDEX UNIQUE SCAN | RCV_SHIPMENT_HEADERS_U1 | 1 | | 1 (0)| 00:00:01 |
|* 63 | INDEX UNIQUE SCAN | RCV_SHIPMENT_LINES_U1 | 1 | 6 | 1 (0)| 00:00:01 |
---------------------------------------------------------------------------------------------------------------------------------------The PGA size is 5gb. What is the cause of this wait event?
baskar.lHi,
How do i resolve this..?
Read from the document Optimizer Selects the Merge Join Cartesian Despite the Hints (Doc ID 457058.1)
| 24 | MERGE JOIN CARTESIAN | | 1 | 18 | 10 (0)| 00:00:01 |
| 25 | TABLE ACCESS FULL | FND_PRODUCT_GROUPS | 1 | 2 | 2 (0)| 00:00:01 |
| 26 | BUFFER SORT | | 1 | 16 | 8 (0)| 00:00:01 |
|* 27 | TABLE ACCESS BY INDEX ROWID| GL_CODE_COMBINATIONS | 1 | 16 | 8 (0)| 00:00:01 |
|* 28 | INDEX RANGE SCAN | JSW_GL_CODE_COMB_SEG_IDX | 10 | | 2 (0)| 00:00:01 |Have set
SQL> alter session set "_optimizer_mjc_enabled"=false ;
|* 21 | HASH JOIN | | 4 | 284 | 139 (1)| 00:00:02 |
|* 22 | TABLE ACCESS BY INDEX ROWID | GL_JE_LINES | 65 | 2730 | 124 (0)| 00:00:02 |
| 23 | NESTED LOOPS | | 75 | 4500 | 134 (0)| 00:00:02 |
| 24 | NESTED LOOPS | | 1 | 18 | 10 (0)| 00:00:01 |
| 25 | TABLE ACCESS FULL | FND_PRODUCT_GROUPS | 1 | 2 | 2 (0)| 00:00:01 |
|* 26 | TABLE ACCESS BY INDEX ROWID| GL_CODE_COMBINATIONS | 1 | 16 | 8 (0)| 00:00:01 |
|* 27 | INDEX RANGE SCAN | JSW_GL_CODE_COMB_SEG_IDX | 10 | | 2 (0)| 00:00:01 |thanks,
baskar.l -
Regarding 'Direct Path Read' waits
As we all know, direct path read waits is a new feature in Oracle 11g. From Oracle Documents or others' articles, when it is full table scan, direct path read occured. But why it occured? I don't know clearly.
Below is Oracle Document description:
http://docs.oracle.com/cd/E18283_01/server.112/e17110/waitevents003.htm#sthref3849
During Direct Path operations the data is asynchronously read from the database files. At some stage the session needs to make sure that all outstanding asynchronous I/O have been completed to disk. This can also happen if during a direct read no more slots are available to store outstanding load requests (a load request could consist of multiple I/Os).
Question:
1. During Direct Path operations the data is asynchronously read from the database files. >> what does this statement mean? what's ''asynchronously read'?
2. describe above description for me in details.
3. who can clearly explain 'why direct path read waits occur' for me?
Thanks in advance.
LonionLonion wrote:
Question:
1. During Direct Path operations the data is asynchronously read from the database files. >> what does this statement mean? what's ''asynchronously read'?
2. describe above description for me in details.
3. who can clearly explain 'why direct path read waits occur' for me?
If you want to get very technical, Frits Hoogland has written lots of stuff about the implementation:
http://fritshoogland.wordpress.com/2013/05/09/direct-path-read-and-fast-full-index-scans/
http://fritshoogland.wordpress.com/2013/01/04/oracle-11-2-and-the-direct-path-read-event/
http://fritshoogland.wordpress.com/2012/12/27/oracle-11-2-0-1-and-the-kfk-async-disk-io-wait-event/
http://www.ukoug.org/what-we-offer/library/about-multiblock-reads/about-multiblock-reads.pdf
Regards
Jonathan Lewis -
Select count(*) from table in oracle 11g with direct path read takes time
select count(*) from table takes long time, even more than couple of hours..
direct path read is the wait event which is almost is at 99%..
can u someone provide some info on this.. on solution.. thankxknowledgespring wrote:
table has millions of records... 130 millions..
select count(*) from BIG_SIZE_TABLE; --- executed in sql plus command prompt.
Rows Execution Plan
0 SELECT STATEMENT MODE: ALL_ROWS
0 SORT (AGGREGATE)
0 TABLE ACCESS MODE: ANALYZED (FULL) OF 'BIG_SIZE_TABLE' (TABLE)
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
SQL*Net message to client 1 0.00 0.00
enq: KO - fast object checkpoint 1 0.01 0.01
Disk file operations I/O 18 0.00 0.00
direct path read 58921 0.34 418.54direct path read time waited is : 58921 total time waited: 418.54
That 418 seconds - not the hours you reported earlier. Is it possible that your connection to the database broke ?
On a typical system, by the way, you can usually turn one direct read for tablescan into 1MB, so your scan seems to have covered about 59 GB, which seems to be in the right sort of ballpark for 130M rows.
we have another query and when we test the query execution using v$sql, is_bind_sensitive =N, how to make is_bind_sensitive=Y all the time.. There is a hint /*+ bind_aware */ - I'd have to check whether or not it's documented at present. It might help.
I would be interested in hearing why you think the hint should be bind sensitive when the optimizer doesn't.
Regards
Jonathan Lewis -
WAIT = 'direct path read temp' in session
Hi;
select * from v$version
Oracle Database 11g Release 11.2.0.1.0 - 64bit Production
In our development system, a query "insert into X" using a couple of session global temporary tables, was running under 5 minuts, is now taking 40 minuts!
Sql Developer Sessions shows a wait: "direct path read temp"
Any hints on that might cause this, and possible solutions?
Trace file of the session looks like this:
*** 2013-03-18 15:56:22.871
WAIT #20: nam='direct path read temp' ela= 106 file number=201 first dba=46685 block cnt=31 obj#=61321 tim=1363614982871399
*** 2013-03-18 15:56:25.354
WAIT #20: nam='direct path read temp' ela= 90 file number=201 first dba=46336 block cnt=31 obj#=61321 tim=1363614985354148
*** 2013-03-18 15:56:28.098
WAIT #20: nam='direct path read temp' ela= 86 file number=201 first dba=46367 block cnt=31 obj#=61321 tim=1363614988098575
*** 2013-03-18 15:56:32.302
WAIT #20: nam='direct path read temp' ela= 112 file number=201 first dba=69438 block cnt=31 obj#=61321 tim=1363614992302296
WAIT #20: nam='direct path read temp' ela= 93 file number=201 first dba=69469 block cnt=31 obj#=61321 tim=1363614992302484
WAIT #20: nam='direct path read temp' ela= 95 file number=201 first dba=68030 block cnt=31 obj#=61321 tim=1363614992302888
WAIT #20: nam='direct path read temp' ela= 93 file number=201 first dba=66719 block cnt=31 obj#=61321 tim=1363614992303265
WAIT #20: nam='direct path read temp' ela= 107 file number=201 first dba=65726 block cnt=31 obj#=61321 tim=1363614992303657
WAIT #20: nam='direct path read temp' ela= 94 file number=201 first dba=64702 block cnt=31 obj#=61321 tim=1363614992304037
WAIT #20: nam='direct path read temp' ela= 97 file number=201 first dba=63709 block cnt=31 obj#=61321 tim=1363614992304421
WAIT #20: nam='direct path read temp' ela= 94 file number=201 first dba=62623 block cnt=31 obj#=61321 tim=1363614992304820
WAIT #20: nam='direct path read temp' ela= 111 file number=201 first dba=61471 block cnt=31 obj#=61321 tim=1363614992305227
WAIT #20: nam='direct path read temp' ela= 121 file number=201 first dba=60606 block cnt=31 obj#=61321 tim=1363614992305764
WAIT #20: nam='direct path read temp' ela= 100 file number=201 first dba=59392 block cnt=31 obj#=61321 tim=1363614992306175
WAIT #20: nam='direct path read temp' ela= 101 file number=201 first dba=58589 block cnt=31 obj#=61321 tim=1363614992306579
WAIT #20: nam='direct path read temp' ela= 98 file number=201 first dba=57503 block cnt=31 obj#=61321 tim=1363614992306965
WAIT #20: nam='direct path read temp' ela= 93 file number=201 first dba=56510 block cnt=31 obj#=61321 tim=1363614992307342
WAIT #20: nam='direct path read temp' ela= 94 file number=201 first dba=55296 block cnt=31 obj#=61321 tim=1363614992307742
WAIT #20: nam='direct path read temp' ela= 96 file number=201 first dba=54272 block cnt=31 obj#=61321 tim=1363614992308149
WAIT #20: nam='direct path read temp' ela= 131 file number=201 first dba=53407 block cnt=31 obj#=61321 tim=1363614992308651
WAIT #20: nam='direct path read temp' ela= 108 file number=201 first dba=52480 block cnt=31 obj#=61321 tim=1363614992309129
WAIT #20: nam='direct path read temp' ela= 99 file number=201 first dba=52511 block cnt=31 obj#=61321 tim=1363614992309273Tkprof output... notice the big values for direct path write temp and direct path read temp values!
OVERALL TOTALS FOR ALL NON-RECURSIVE STATEMENTS
callcount cpu elapsed disk query current rows
Parse 2 0.17 0.18 0 0 0 0
Execute 2 0.00 0.00 0 0 0 0
Fetch 4 206.24 207.66 18960 755 21 8
total 8 206.42 207.84 18960 755 21 8
Misses in library cache during parse: 2
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
SQL*Net message to client 5 0.00 0.00
SQL*Net message from client 5 11.01 19.27
db file sequential read 6 0.00 0.00
Disk file operations I/O 15 0.00 0.00
asynch descriptor resize 84 0.00 0.00
direct path write temp 1264 0.19 1.25
direct path read temp 1264 0.00 0.04
control file sequential read 42 0.00 0.00
db file single write 3 0.00 0.00
control file parallel write 9 0.00 0.00
rdbms ipc reply 2 0.00 0.00
local write wait 12 0.00 0.00
log file sync 2 0.00 0.00
OVERALL TOTALS FOR ALL RECURSIVE STATEMENTS
call count cpu elapsed disk query current rows
Parse 85 0.04 0.04 0 0 0 0
Execute 899 0.18 0.24 22 47 7 4
Fetch 1393 0.04 0.69 204 3200 0 7002
total 2377 0.28 0.98 226 3247 7 7006
Misses in library cache during parse: 55
Misses in library cache during execute: 51
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
db file sequential read 206 0.03 0.65
latch: shared pool 4 0.00 0.00
Disk file operations I/O 2 0.00 0.00
db file scattered read 3 0.03 0.04
5 user SQL statements in session.
896 internal SQL statements in session.
901 SQL statements in session.
Trace file: SXDB_ora_25080.trc
Trace file compatibility: 11.1.0.7
Sort options: default
1 session in tracefile.
5 user SQL statements in trace file.
896 internal SQL statements in trace file.
901 SQL statements in trace file.
41 unique SQL statements in trace file.
21517 lines in trace file.
217 elapsed seconds in trace file.
Edited by: PauloSMO on 19/Mar/2013 11:36 -
Direct Path Reads instead of Sequential Reads for index range scan
Database is 11.2. I have two development schemas, with the same table loaded in each schema - a 5 million row table. The execution path for the sql statement is the same against both tables; it's doing an index range scan.
But it would appear Oracle performs a direct path read against one schema, and performs sequential reads against the other schema. I don't understand why I'm seeing different behavior when the execution plan is the same. Any ideas? These are two different schemas in the same database.There is not enough information.So you even these tables located same database and you gathered statistics it is not mean both run time wait event statistics must be same.Really they are different tables.If both query use INDEX RANGE SCAN the it is not mean these plans are same.What about table and their index statistics? are they same? for example num_row or num_blocks of both tables are same? also about indexes.In additionally if you want to get exact reason you can enable sql trace(using dbms_monitor or setting sql_trace parameter to true according session) and need analyze result trace file using tkprof utility.In additionally in 11g here when query execution time oracle automatically choose direct read path(serial) based on size of tables and size of buffer cache(also here is available some hidden parameter to controlling this behavior).
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