Understanding Physical Reads

Hello everyone,
I'm trying to understand about physical reads statistics.
we have a few statistics related to this.
They are physical reads, physical reads cache, physical reads cache prefetch, physical reads direct, physical reads direct (lob), physical reads direct temporary tablespace, and physical reads prefetch warmup.
From all those statistics, I thought that physical reads should be like the total of the rest of the other statistics.
However, when I looked at the actual AWR report I collected from a production database here, it seems physical reads value is only similar to the value of physical reads cache + physical reads direct.
I wonder about the rest of the statistics related to this physical reads, I thought that physical reads statistics is like the grand total of all those physical reads, however that doesn't seems to be the case. How do I interpret these statistcs?
Appreciate if you can explain how these statistics can be used when understanding a database performance.
Thank you,
Adhika

Similar Messages

Consistent gets and physical reads

Hi all,
I am tuning a DM SQL query, by comparing execution plans with STAR TRANSFORMATION enabled or disabled. I got the following results:
STAR TRANSFORMATION ON
74889 consistent gets
254365 physical reads
STAR TRANSFORMATION OFF
1945892 consistent gets
168028 physical reads
I thought a physical read would be counted as a logical read as well, because the data block would be read from disk (1 physical IO), placed in the buffer cache and then read from there (1 more logical IO or consistent get).
So, one physical IO does not cause a logical IO?
Thanks!
Edited by: user10634835 on 12-Jul-2011 08:40

But shouldn't consistent gets be >= physical reads (Since, as per my understanding, 1 PIO causes at least 1 LIO)? In this case it is not.
74889 consistent gets
254365 physical readsJust clarifying for my knowledge.
regards

Query on data dictionary results in large number of physical reads

I don't understand why I am getting 80,000 physicals for this query. I am not looking for help re-writing this. I just don't understand why I would hit the disk at all.
My understanding had been that v$views where sql structures that pointed to x$tables. These x$tables are sql structures.
underneath, the x$tables were linked lists stored in memory. This is why when you bounce the database, all the data, gets reset. Since it is not saved to disk.
I am doing a simple insert/select off of v$open_cursor that is resulting in 80,000+ physical reads. I am posting the tkprof. It is all from v$open_cursor.
mysid_table has 6 records. It is 1 mb in size
if I index mysid_table.sid the query reduces to 20,000 physical reads. (but all the physical reads are on v$session_event)
the sequence number I am passing returns 2 SIDs
insert into my_save_table
select *
from v$session_event
where sid in (select sid
from my_sid_table
where id = vseq);
vrowcount := sql%rowcount;
call     count       cpu    elapsed       disk      query    current        rows
Parse        1      0.01       0.01          0          0          0           0
Execute      1     31.70      47.57      88570         22          0           1
Fetch        0      0.00       0.00          0          0          0           0
total        2     31.71      47.58      88570         22          0           1
Misses in library cache during parse: 1
Optimizer mode: CHOOSE
Parsing user id: 22
Elapsed times include waiting on following events:
Event waited on                             Times   Max. Wait Total Waited
----------------------------------------   Waited ---------- ------------
latch: row cache objects                        1        0.00          0.00
log file sync                                   1        0.00          0.00
SQL*Net message to client                       1        0.00          0.00
SQL*Net message from client                     1        0.00          0.00
********************************************************************************

It seems like there is some missing information.
You have a wait for a log file sync, but no commit.
Your table my_sid_table is 1 MB for only 6 records?
Does the target table you are inserting into (my_save_table) have indexes on it?

No of physical reads of buffers from disk on PROD and Clone has huge differ

Please help !
I am having a problem interpreting a tkprof report.
I am executing the same statement below in PROD and Clone of PROD.
What I do not understand why the tkprof report shows huge difference in disk reads for same executions from PROD and Clone of PROD. I.e. first execution disk reads = 757187 , second = 6.
I expected to see Similar disk reads in the second execution also.The data it fetches is same in both the Instances.
Statment
SELECT NVL(SUM(RG_OTH.DEBIT),0),NVL(SUM(RG_OTH.CREDIT),0)
FROM
JA_IN_PLA PLA,JAI_RG_OTHERS RG_OTH,HR_ALL_ORGANIZATION_UNITS HOU,
HR_LOCATIONS LOC,JA_IN_HR_ORGANIZATION_UNITS HR_ORG WHERE 1 = 1 AND
PLA.ORGANIZATION_ID = :b1 AND TRUNC(PLA.CREATION_DATE) >= :b2 AND
TRUNC(PLA.CREATION_DATE) <= :b3 AND HOU.ORGANIZATION_ID =
PLA.ORGANIZATION_ID AND LOC.LOCATION_ID = PLA.LOCATION_ID AND
HR_ORG.ORGANIZATION_ID = PLA.ORGANIZATION_ID AND HR_ORG.LOCATION_ID =
PLA.LOCATION_ID AND TRANSACTION_ID = 19 AND INVENTORY_ITEM_ID != 0 AND
NVL(ROUNDING_ID,1) != -1 AND RG_OTH.SOURCE_REGISTER_ID = PLA.REGISTER_ID
AND RG_OTH.SOURCE_REGISTER = 'PLA' AND RG_OTH.TAX_TYPE IN (
'EXCISE_EDUCATION_CESS' )
Tkproff from PROD.
call count cpu elapsed disk query current rows
Parse 1 0.01 0.01 0 0 0 0
Execute 1 0.04 0.03 0 0 0 0
Fetch 1 973.41 1724.95 757187 789442 0 1
total 3 973.46 1725.01 757187 789442 0 1
Tkproff from CLONE of PROD.
call count cpu elapsed disk query current rows
Parse 1 0.06 0.05 1 789 0 0
Execute 1 0.00 0.00 0 0 0 0
Fetch 1 0.73 0.72 6 30594 0 1
total 3 0.79 0.78 7 31383 0 1

wins wrote:
SELECT NVL(SUM(RG_OTH.DEBIT),0),NVL(SUM(RG_OTH.CREDIT),0)
FROM
JA_IN_PLA PLA,JAI_RG_OTHERS RG_OTH,HR_ALL_ORGANIZATION_UNITS HOU,
HR_LOCATIONS LOC,JA_IN_HR_ORGANIZATION_UNITS HR_ORG WHERE 1 = 1 AND
PLA.ORGANIZATION_ID = :b1 AND TRUNC(PLA.CREATION_DATE) >= :b2 AND
TRUNC(PLA.CREATION_DATE) <= :b3 AND HOU.ORGANIZATION_ID =
PLA.ORGANIZATION_ID AND LOC.LOCATION_ID = PLA.LOCATION_ID AND
HR_ORG.ORGANIZATION_ID = PLA.ORGANIZATION_ID AND HR_ORG.LOCATION_ID =
PLA.LOCATION_ID AND TRANSACTION_ID = 19 AND INVENTORY_ITEM_ID != 0 AND
NVL(ROUNDING_ID,1) != -1 AND RG_OTH.SOURCE_REGISTER_ID = PLA.REGISTER_ID
AND RG_OTH.SOURCE_REGISTER = 'PLA' AND RG_OTH.TAX_TYPE IN (
'EXCISE_EDUCATION_CESS' )
Tkproff from PROD.
call     count       cpu    elapsed       disk      query    current        rows
Parse        1      0.01       0.01          0          0          0           0
Execute      1      0.04       0.03          0          0          0           0
Fetch        1    973.41    1724.95     757187     789442          0           1
total        3    973.46    1725.01     757187     789442          0           1
Tkproff from CLONE of PROD.
call     count       cpu    elapsed       disk      query    current        rows
Parse        1      0.06       0.05          1        789          0           0
Execute      1      0.00       0.00          0          0          0           0
Fetch        1      0.73       0.72          6      30594          0           1
total        3      0.79       0.78          7      31383          0           1
As others have pointed out, this looks like a change in execution plan. At a guess, the PROD database is doing a tablescan somewhere (physical reads is approximately equal to logical reads is a pointer).
There are many reasons why this could happen, continuing with the guesswork - we note that the statement was re-optimised (hard parsed) in the clone, but used an existing cursor in production (logical I/O = 0 in prod, 789 in clone). So the plan you got in the clone was the one that Oracle thought best for the inputs you had supplied. The plan in prod could have been produced as the response to a completely different set of input; since you have two bind variables applied to a range based predicated and one bind variable with equality it's possible that you have a histogram that makes a difference on the equality column, alternatively the range of dates used to generate the original plan was very different from the range used in the test.
Regards
Jonathan Lewis
http://jonathanlewis.wordpress.com
Author: <b><em>Oracle Core</em></b>

View to find Physical read and Write per hour

HI,
My oracle database is running with 11.2.0.3 and we are analysing the database. we would like to understand what the average load time per hour is for a database under normal circumstances e.g. 5 TB /Hr ?
What I want to know is, Is it possible to find the amount physical reads and writes happened per hour basis on database. Is there any view to find this ?
Thanks,
Kesav.

1e36fe40-5d07-412e-8ed2-704c647ed7a7 wrote:
HI,
My oracle database is running with 11.2.0.3 and we are analysing the database. we would like to understand what the average load time per hour is for a database under normal circumstances e.g. 5 TB /Hr ?
What I want to know is, Is it possible to find the amount physical reads and writes happened per hour basis on database. Is there any view to find this ?
Thanks,
Kesav.
number of READ operations?
number of bytes read?
SQL> desc v$IOSTAT_FILE
Name                                      Null?    Type
FILE_NO                                            NUMBER
FILETYPE_ID                                        NUMBER
FILETYPE_NAME                                      VARCHAR2(28)
SMALL_READ_MEGABYTES                               NUMBER
SMALL_WRITE_MEGABYTES                              NUMBER
LARGE_READ_MEGABYTES                               NUMBER
LARGE_WRITE_MEGABYTES                              NUMBER
SMALL_READ_REQS                                    NUMBER
SMALL_WRITE_REQS                                   NUMBER
SMALL_SYNC_READ_REQS                               NUMBER
LARGE_READ_REQS                                    NUMBER
LARGE_WRITE_REQS                                   NUMBER
SMALL_READ_SERVICETIME                             NUMBER
SMALL_WRITE_SERVICETIME                            NUMBER
SMALL_SYNC_READ_LATENCY                            NUMBER
LARGE_READ_SERVICETIME                             NUMBER
LARGE_WRITE_SERVICETIME                            NUMBER
ASYNCH_IO                                          VARCHAR2(9)
ACCESS_METHOD                                      VARCHAR2(11)
RETRIES_ON_ERROR                                   NUMBER
SQL>

SGA size is 1 GB free but oracle starts physical read/write,why ?

Dear Friends ,
In my production server I observe that it takes the the data from the HDD where my SGA is still 1 GB free .
As far I know , In oracle , when the allocated SGA size is filled up then it reads the data from the HDD which is called "physical read/write " . I am using oracle 10g database . In performance tab(From Oracle 10g OEM) , when I see that oracle starts to read the physical data , at that moment I run the following query :
select sum(bytes)/1024/1024 " SGA size used in MB"
from v$sgastat
where name!='free memory';
and I found that still 1 GB memory are still free in the SGA .
In this moment , I want to know , is it possible to start the physical read / write while the SGA size are still free ?
Edited by: shipon_97 on Mar 24, 2009 10:45 AM

shipon_97,
Your understanding is wrong. From your previous posts it appears you never read the concepts manual.
Begging on my knees PLEASE READ IT and stop asking doc questions.
Sybrand Bakker
Senior Oracle DBA

Define - consistent_gets, db_block_gets, physical reads

Hi
Can anybody explain the components we use for
Buffer Hit Ratio consistent_gets, db_block_gets,
physical reads ? They all measured in terms of blocks
or no of counts of reads/fetches ?
Still I am not clear with consistent_gets and db_block_gets
I have read some articles of good authors.
They say db_block_gets consists of physical/logical
gets. If they represent different units of measurements
how can we arrive at Hit ratio ?
S.D.RAVICHANDRAN
Verizon.

Hi
I browsed ora-faq site and got the below answer :
Consistent get = The blocks which is bound to change
dynamically due to updations and in order to retain
its previous image it has to visit undo segment and
maintain its originallity. It involves CPU. That's why
sometimes LIO is costly and engages CPU.
db_block_get = No above change happens.
This is my simple understanding. You can add if
you deem fit.
Ravichandran
Verizon.

9582.69043 gigabytes of physical read total bytes and increasing!

In EM
Database Instance: PROD > Top Activity > I got following
physical read total bytes     62763565056     10289335500800     4183122176
cell physical IO interconnect bytes     62763565056     10289335500800     4183122176
physical read bytes     62763565056     10289335500800     4183122176
And the session is running following update procedure:
declare
FM_BBBB MT.BBBB_CODE%TYPE;
l_start NUMBER;
cursor code_upd is select /*+ parallel(FM_KWT_POP_BBBB_MISMATCH, 10) */ DDD_CID, DDD_BBBB, CCCC_BBBB from MT_MISMATCH;
begin
-- Time regular updates.
l_start := DBMS_UTILITY.get_time;
FOR rec IN code_upd LOOP
update /*+ parallel(MT, 10) nologging */ MT
set BBBB_code = rec.CCCC_BBBB
where source= 0
and cid_no = rec.DDD_CID
and BBBB_code = rec.DDD_BBBB;
commit;
END LOOP;
DBMS_OUTPUT.put_line('Bulk Updates : ' || (DBMS_UTILITY.get_time - l_start));
end;
There are 9.5 million records in MT but source=0 have only 3 million records and 376K records in MT_MISMATCH, What I don't understand why this is taking so much of time and so many bytes read? Both Tables are analyzed before running this procedure.
Can someone shed some light on this? Is there any better way of doing the same job?

Nabeel Khan wrote:
In EM
Database Instance: PROD > Top Activity > I got following
physical read total bytes     62763565056     10289335500800     4183122176
cell physical IO interconnect bytes     62763565056     10289335500800     4183122176
physical read bytes     62763565056     10289335500800     4183122176
And the session is running following update procedure:
declare
FM_BBBB MT.BBBB_CODE%TYPE;
l_start NUMBER;
cursor code_upd is select /*+ parallel(FM_KWT_POP_BBBB_MISMATCH, 10) */ DDD_CID, DDD_BBBB, CCCC_BBBB from MT_MISMATCH;
begin
-- Time regular updates.
l_start := DBMS_UTILITY.get_time;
FOR rec IN code_upd LOOP
update /*+ parallel(MT, 10) nologging */ MT
set BBBB_code = rec.CCCC_BBBB
where source= 0
and cid_no = rec.DDD_CID
and BBBB_code = rec.DDD_BBBB;
commit;
END LOOP;
DBMS_OUTPUT.put_line('Bulk Updates : ' || (DBMS_UTILITY.get_time - l_start));
end;
There are 9.5 million records in MT but source=0 have only 3 million records and 376K records in MT_MISMATCH, What I don't understand why this is taking so much of time and so many bytes read? Both Tables are analyzed before running this procedure.
Can someone shed some light on this? Is there any better way of doing the same job?Lots of badness going on here.
1) looping / procedural code where none is needed.
2) commit within the loop, one of the worst evils of all in Oracle. Please read this
http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:2680799800346456179
I'd look into rewriting this as a single SQL (maybe merge) statement. Or at worst .. a bulk process utilizing collections and FORALL's.

What causes BUFFER GETS and PHYSICAL READS in INSERT operation to be high?

Hi All,
Am performing a huge number of INSERTs to a newly installed Oracle XE 10.2.0.1.0 on Windows. There is no SELECT statement running, but just INSERTs one after the other of 550,000 in count. When I monitor the SESSION I/O from Home > Administration > Database Monitor > Sessions, I see the following stats:
BUFFER GETS = 1,550,560
CONSISTENT GETS = 512,036
PHYSICAL READS = 3,834
BLOCK CHANGES = 1,034,232
The presence of 2 stats confuses. Though the operation is just INSERT in database for this session, why should there be BUFFER GETS of this magnitude and why should there by PHYSICAL READS. Aren't these parameters for read operations? The BLOCK CHANGES value is clear as there are huge writes and the writes change these many blocks. Can any kind soul explain me what causes there parameters to show high value?
The total columns in the display table are as follows (from the link mentioned above)
1. Status
2. SID
3. Database Users
4. Command
5. Time
6. Block Gets
7. Consistent Gets
8. Physical Reads
9. Block Changes
10. Consistent Changes
What does CONSISTENT GETS and CONSISTENT CHANGES mean in a typical INSERT operation? And does someone know which all tables are involved in getting these values?
Thank,
...

Flake wrote:
Hans, gracias.
The table just have 2 columns, both of which are varchar2 (500). No constraints, no indexes, neither foreign key references are in place. The total size of RAM in system is 1GB, and yes, there are other GUI's going on like Firefox browser, notepad and command terminals.
But, what does these other applications have to do with Oracle BUFFER GETS, PHYSICAL READS etc.? Awaiting your reply.Total RAM is 1GB. If you let XE decide how much RAM is to be allocated to buffers, on startup that needs to be shared with any/all other applications. Let's say that leaves us with, say 400M for the SGA + PGA.
PGA is used for internal stuff, such as sorting, which is also used in determing the layout of secondary facets such as indexes and uniqueness. Total PGA usage varies in size based on the number of connections and required operations.
And then there's the SGA. That needs to cover the space requirement for the data dictionary, any/all stored procedures and SQL statements being run, user security and so on. As well as the buffer blocks which represent the tablespace of the database. Since it is rare that the entire tablespace will fit into memory, stuff needs to be swapped in and out.
So - put too much space pressure on the poor operating system before starting the database, and the SGA may be squeezed. Put that space pressure on the system and you may enbd up with swapping or paging.
This is one of the reasons Oracle professionals will argue for dedicated machines to handle Oracle software.

High no. of physical reads of a query in statspack report

we have a Oracle database 9.2.0.6 on solaris box....
SQL ordered by Reads for DB: ic Instance: ic12 Snaps: 19 -20
-> End Disk Reads Threshold:      1000
                                                     CPU      Elapsd
Physical Reads Executions Reads per Exec %Total Time (s) Time (s) Hash Value
      1,103,253           77       14,328.0   53.1 1641.98 11428.17 3825541888
Module: w3wp.exe
select MRH_MRN,DECODE(MRH_SEX,'M','MALE','FEMALE') AS SEX, trim
((mrh_sur_name||' '||mrh_first_name||' '||mrh_middle_name)) as M
EMNAME, decode(nvl(mrh_fellow_status_yn,'333'),'Y','FCA','ACA')
AS ACA_FCA, DECODE(MRH_RESI_STATUS,'I',MRH_PROF_ADDR_LINE_1,'A',
MRH_RES_ADDR_LINE_1) AS L_ADD1, DECODE(MRH_RESI_STATUS,'I',MRH_Pexplain plan
SQL> explain plan for select MRH_MRN,DECODE(MRH_SEX,'M','MALE','FEMALE') AS SEX
, trim((mrh_sur_name||' '||mrh_first_name||' '||mrh_middle_name)) as MEMNAME, de
code(nvl(mrh_fellow_status_yn,'333'),'Y','FCA','ACA')AS ACA_FCA, DECODE(MRH_RESI
_STATUS,'I',MRH_PROF_ADDR_LINE_1,'A',
2 MRH_RES_ADDR_LINE_1) AS L_ADD1, DECODE(MRH_RESI_STATUS,'I',MRH_PROF_ADDR_LI
NE_2,'A',MRH_RES_ADDR_LINE_2) AS L_ADD2, DECODE(MRH_RESI_STATUS,'I',MRH_PROF_ADD
R_LINE_3,'A',MRH_RES_ADDR_LINE_3) ASL_ADD3, DECODE(MRH_RESI_STATUS,'I',MRH_PROF_
ADDR_LINE_4,'A',
3 MRH_RES_ADDR_LINE_4) AS L_ADD4, DECODE(MRH_RESI_STATUS,'I',a.city_name,'A',
C.CITY_NAME) AS L_CITY, DECODE(MRH_RESI_STATUS,'I',MRH_PROF_ZIP_POSTAL_CODE,'A',
MRH_RES_ZIP_POSTAL_CODE) AS L_PIN, DECODE(MRH_RESI_STATUS,'I',b.cou_name,'A',D.C
OU_NAME) as L_Country,
4 DECODE(MRH_RESI_STATUS,'I','NOT APPLICABLE',MRH_PROF_ADDR_LINE_1)AS R_ADD1,
DECODE(MRH_RESI_STATUS,'I',' ',MRH_PROF_ADDR_LINE_2)AS R_ADD2, DECODE(MRH_RESI_
STATUS,'I',' ',MRH_PROF_ADDR_LINE_3)
5 AS R_ADD3, DECODE(MRH_RESI_STATUS,'I',' ',MRH_PROF_ADDR_LINE_4)AS R_ADD4, D
ECODE(MRH_RESI_STATUS,'I',' ','A',A.CITY_NAME) AS R_CITY, DECODE(MRH_RESI_STATUS
,'I',' ','A',MRH_PROF_ZIP_POSTAL_CODE) AS R_PIN, DECODE(MRH_RESI_STATUS,'I',' ',
'A',B.COU_NAME) as
6 R_Country, decode(nvl(mrh_mem_sub_status,'555'),'26','EXPIRED','') as sub_s
tatus, decode(nvl(mrh_mem_status,'777'),'1','ACTIVE','2','REMOVED') as mem_statu
s,mrh_resi_status, DECODE(MRH_COP_STATUS,'1',DECODE(MRH_COP_TYPE ,'13','FULLTIME
-COP','1',
7 'FULLTIME-COP', '12','PARTTIME-COP','2','PARTTIME-COP'),'NOT HOLDING COP')
AS COP_STATUS, TO_CHAR(MRH_ENROL_DT,'RRRR') AS ASSO_YR,TO_CHAR(MRH_FELLOW_DT,'RR
RR') AS FELLOW_YR from om_mem_reg_head,om_city A,
8 om_country B,om_city C,om_country D where mrh_doc_status=5 and mrh_prof_
city_code=A.City_code(+) and mrh_prof_cou_code=B.cou_code(+) and mrh_res_city_c
ode=C.City_code(+) and mrh_res_cou_code=D.cou_code(+) and trim((mrh_sur_name||'
'||mrh_first_name||
9 ''||mrh_middle_name)) like upper('%%') ORDER BY trim((mrh_sur_name||' '||m
rh_first_name||' '||mrh_middle_name))
10 ;
Explained.
SQL> select * from table(dbms_xplan.displaY());
PLAN_TABLE_OUTPUT
| Id | Operation              | Name            | Rows | Bytes |TempSpc| Cost
|
|   0 | SELECT STATEMENT       |                  | 2870 |   762K|       | 202
PLAN_TABLE_OUTPUT
8 |
|   1 | SORT ORDER BY         |                  | 2870 |   762K| 1592K| 202
8 |
|   2 |   NESTED LOOPS OUTER   |                  | 2870 |   762K|       | 190
2 |
|   3 |    NESTED LOOPS OUTER |                  | 2870 |   714K|       | 190
2 |
PLAN_TABLE_OUTPUT
|   4 |     HASH JOIN OUTER    |                  | 2870 |   667K|       | 190
2 |
|   5 |      HASH JOIN OUTER   |                  | 2870 |   616K|       | 189
2 |
|   6 |       TABLE ACCESS FULL| OM_MEM_REG_HEAD | 2870 |   566K|       | 188
2 |
|   7 |       TABLE ACCESS FULL| OM_COUNTRY       |   677 | 12186 |       |
4 |
PLAN_TABLE_OUTPUT
|   8 |      TABLE ACCESS FULL | OM_COUNTRY       |   677 | 12186 |       |
4 |
|   9 |     INDEX UNIQUE SCAN | CITY_CODE_PK     |     1 |    17 |       |
|
| 10 |    INDEX UNIQUE SCAN   | CITY_CODE_PK     |     1 |    17 |       |
|
PLAN_TABLE_OUTPUT
Note: cpu costing is off, PLAN_TABLE' is old version
18 rows selected.
SQL>Please suggest me whjat cab done to overcome the same
Edited by: user00726 on Feb 3, 2009 5:03 AM

SQL> show arraysize
arraysize 15
SQL>should i set SDU parameter in tnsnames and listener.ora
for more info related to the same...pls do visit the below thread:
n/w perfromance related problem

Query tuning-how to reduce physical reads-help me

1* select * from masterbillingInvoiceview Where SiteIID =300964 and InvoiceID like '%' order by Invoice asc
SQL> /
33 rows selected.
Elapsed: 00:00:00.34
Execution Plan
Plan hash value: 352896138
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
| 0 | SELECT STATEMENT | | 16 | 6304 | 341 (3)| 00:00:05 |
| 1 | SORT ORDER BY | | 16 | 6304 | 341 (3)| 00:00:05 |
| 2 | TABLE ACCESS BY INDEX ROWID | ADDRESS | 1 | 48 | 2 (0)| 00:00:01
| 3 | NESTED LOOPS | | 16 | 6304 | 340 (3)| 00:00:05 |
| 4 | NESTED LOOPS | | 16 | 5536 | 316 (3)| 00:00:04 |
|* 5 | HASH JOIN OUTER | | 16 | 5168 | 308 (3)| 00:00:04 |
|* 6 | HASH JOIN | | 16 | 4992 | 302 (3)| 00:00:04 |
|* 7 | HASH JOIN | | 16 | 4752 | 298 (3)| 00:00:04 |
| 8 | NESTED LOOPS | | 17 | 4828 | 44 (0)| 00:00:01 |
| 9 | NESTED LOOPS | | 17 | 3451 | 35 (0)| 00:00:01 |
| 10 | NESTED LOOPS OUTER | | 1 | 91 | 2 (0)| 00:00:01 |
| 11 | TABLE ACCESS BY INDEX ROWID| SITEMASTER | 1 | 74 | 1 (0)| 00:00:01 |
|* 12 | INDEX UNIQUE SCAN | PK_SITEMASTER | 1 | | 1 (0)| 00:00:01 |
| 13 | TABLE ACCESS BY INDEX ROWID| INVGROUPS | 1735 | 29495 | 1 (0)| 00:00:01 |
|* 14 | INDEX UNIQUE SCAN | PK_INVGROUPS | 1 | | 1 (0)| 00:00:01 |
|* 15 | TABLE ACCESS BY INDEX ROWID | INVOICEHEAD | 17 | 1904 | 33 (0)| 00:00:01 |
|* 16 | INDEX RANGE SCAN | IDX_INVOICEHEADSITEIID | 271 | | 1 (0)| 00:00:01 |
| 17 | TABLE ACCESS BY INDEX ROWID | CUSTOMER | 1 | 81 | 1 (0)| 00:00:01 |
|* 18 | INDEX UNIQUE SCAN | PK_CUSTOMER | 1 | | 1 (0)| 00:00:01 |
| 19 | VIEW | | 35844 | 455K| 254 (3)| 00:00:04 |
| 20 | HASH GROUP BY | | 35844 | 455K| 254 (3)| 00:00:04 |
| 21 | TABLE ACCESS FULL | CONTACT | 56100 | 712K| 250 (1)| 00:00:03 |
| 22 | VIEW | index$_join$_009 | 7 | 105 | 3 (0)| 00:00:01 |
|* 23 | HASH JOIN | | | | | |
| 24 | INDEX FAST FULL SCAN | IDX_PAYMENTTERMSID | 7 | 105 | 1 (0)| 00:00:01
| 25 | INDEX FAST FULL SCAN | PK_PAYMENTTERMS | 7 | 105 | 1 (0)| 00:00:01
| 26 | VIEW | index$_join$_011 | 1428 | 15708 | 6 (0)| 00:00:01 |
|* 27 | HASH JOIN | | | | | |
| 28 | INDEX FAST FULL SCAN | PK_EMPLOYEE | 1428 | 15708 | 3 (0)| 00:00:01 |
| 29 | INDEX FAST FULL SCAN | IDX_EMPLOYEEEMPLOYEEID | 1428 | 15708 | 3 (0)| 00:00:01
| 30 | TABLE ACCESS BY INDEX ROWID | CONTACT | 1 | 23 | 1 (0)| 00:00:
|* 31 | INDEX UNIQUE SCAN | PK_CONTACT | 1 | | 1 (0)| 00:00:01 |
|* 32 | INDEX RANGE SCAN | PK_ADDRESS | 1 | | 1 (0)| 00:00:01 |
Predicate Information (identified by operation id):
5 - access("A"."CREATEDBY"="J"."EMPIID"(+))
6 - access("A"."TERMSIID"="H"."PAYMENTTERMSIID")
7 - access("D"."CUSTOMERIID"="F"."CUSTOMERIID")
12 - access("B"."SITEIID"=300964)
14 - access("B"."PARENTIID"="I"."GROUPIID"(+))
15 - filter("A"."TYPE"=4 AND "A"."INVOICEID" LIKE '%')
16 - access("A"."SITEIID"=300964)
18 - access("A"."BILLINGCUSTOMERIID"="D"."CUSTOMERIID")
23 - access(ROWID=ROWID)
27 - access(ROWID=ROWID)
31 - access("F"."CONTACTIID"="G"."CONTACTIID")
32 - access("E"."ADDRESSIID"=NVL("D"."BILLINGADDRESSIID","D"."ADDRESSIID"))
Statistics
107 recursive calls
0 db block gets
2819 consistent gets
0 physical reads
0 redo size
6586 bytes sent via SQL*Net to client
356 bytes received via SQL*Net from client
4 SQL*Net roundtrips to/from client
1 sorts (memory)
0 sorts (disk)
33 rows processed
SQL> ed
Wrote file afiedt.buf
1* select * from masterbillingInvoiceview Where SiteIID =300964 and InvoiceID like '%%%' order by Invoice asc
SQL> /
33 rows selected.
Elapsed: 00:06:15.23
Execution Plan
Plan hash value: 1828716447
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
| 0 | SELECT STATEMENT | | 2 | 964 | 295 (3)| 00:00:04 |
|* 1 | FILTER | | | | | |
| 2 | SORT GROUP BY | | 2 | 964 | 295 (3)| 00:00:04 |
| 3 | MERGE JOIN CARTESIAN | | 72315 | 33M| 291 (1)| 00:00:04 |
| 4 | TABLE ACCESS BY INDEX ROWID | ADDRESS | 1 | 52 | 2 (0)| 00:00:01 |
| 5 | NESTED LOOPS | | 1 | 447 | 41 (0)| 00:00:01 |
| 6 | NESTED LOOPS | | 1 | 395 | 40 (0)| 00:00:01 |
| 7 | NESTED LOOPS | | 1 | 382 | 38 (0)| 00:00:01 |
| 8 | NESTED LOOPS OUTER | | 1 | 289 | 37 (0)| 00:00:01 |
| 9 | NESTED LOOPS | | 1 | 266 | 36 (0)| 00:00:01 |
| 10 | NESTED LOOPS | | 1 | 239 | 35 (0)| 00:00:01 |
| 11 | NESTED LOOPS OUTER | | 1 | 115 | 2 (0)| 00:00:01 |
| 12 | TABLE ACCESS BY INDEX ROWID| SITEMASTER | 1 | 86 | 1 (0)| 00:00:01 |
|* 13 | INDEX UNIQUE SCAN | PK_SITEMASTER | 1 | | 1 (0)| 00:00:01 |
| 14 | TABLE ACCESS BY INDEX ROWID| INVGROUPS | 1735 | 50315 | 1 (0)| 00:00:01 |
|* 15 | INDEX UNIQUE SCAN | PK_INVGROUPS | 1 | | 1 (0)| 00:00:01 |
|* 16 | TABLE ACCESS BY INDEX ROWID | INVOICEHEAD | 1 | 124 | 33 (0)| 00:00:01 |
|* 17 | INDEX RANGE SCAN | IDX_INVOICEHEADSITEIID | 271 | | 1 (0)| 00:00:01 |
| 18 | TABLE ACCESS BY INDEX ROWID | PAYMENTTERMS | 1 | 27 | 1 (0)| 00:00:01 |
|* 19 | INDEX UNIQUE SCAN | PK_PAYMENTTERMS | 1 | | 1 (0)| 00:00:01 |
| 20 | TABLE ACCESS BY INDEX ROWID | EMPLOYEE | 1 | 23 | 1 (0)| 00:00:01 |
|* 21 | INDEX UNIQUE SCAN | PK_EMPLOYEE | 1 | | 1 (0)| 00:00:01 |
| 22 | TABLE ACCESS BY INDEX ROWID | CUSTOMER | 1 | 93 | 1 (0)| 00:00:01 |
|* 23 | INDEX UNIQUE SCAN | PK_CUSTOMER | 1 | | 1 (0)| 00:00:01 |
| 24 | TABLE ACCESS BY INDEX ROWID | CONTACT | 1 | 13 | 2 (0)| 00:00:01 |
|* 25 | INDEX RANGE SCAN | IDX_CONTACTCUSTOMERIID | 2 | | 1 (0)| 00:00:01 |
|* 26 | INDEX RANGE SCAN | PK_ADDRESS | 1 | | 1 (0)| 00:00:01 |
| 27 | BUFFER SORT | | 56100 | 1917K| 294 (3)| 00:00:04 |
| 28 | TABLE ACCESS FULL | CONTACT | 56100 | 1917K| 250 (1)| 00:00:03 |
Predicate Information (identified by operation id):
1 - filter("G"."CONTACTIID"=MAX("CONTACTIID"))
13 - access("B"."SITEIID"=300964)
15 - access("B"."PARENTIID"="I"."GROUPIID"(+))
16 - filter("A"."TYPE"=4 AND "A"."INVOICEID" LIKE '%%%')
17 - access("A"."SITEIID"=300964)
19 - access("A"."TERMSIID"="H"."PAYMENTTERMSIID")
21 - access("A"."CREATEDBY"="J"."EMPIID"(+))
23 - access("A"."BILLINGCUSTOMERIID"="D"."CUSTOMERIID")
25 - access("D"."CUSTOMERIID"="CUSTOMERIID")
filter("CUSTOMERIID" IS NOT NULL)
26 - access("E"."ADDRESSIID"=NVL("D"."BILLINGADDRESSIID","D"."ADDRESSIID"))
Statistics
1952 recursive calls
78 db block gets
4649 consistent gets
236151 physical reads
0 redo size
6586 bytes sent via SQL*Net to client
356 bytes received via SQL*Net from client
4 SQL*Net roundtrips to/from client
1 sorts (memory)
1 sorts (disk)
33 rows processed
this is the execution plan of my one query with a small difference, bt there is large diffference in physical reads..
can anyone help me out of this
thanks
aju

Hi,
Can you please format your explain plan using
{ code } --without space
Explain plan
{ code } -- without any space
What is your DB version?
There are differences in access and filter criteria...
-- FRIST QUERY
5 - access("A"."CREATEDBY"="J"."EMPIID"(+))
6 - access("A"."TERMSIID"="H"."PAYMENTTERMSIID")
7 - access("D"."CUSTOMERIID"="F"."CUSTOMERIID")
12 - access("B"."SITEIID"=300964)
14 - access("B"."PARENTIID"="I"."GROUPIID"(+))
15 - filter("A"."TYPE"=4 AND "A"."INVOICEID" LIKE '%')
16 - access("A"."SITEIID"=300964)
18 - access("A"."BILLINGCUSTOMERIID"="D"."CUSTOMERIID")
23 - access(ROWID=ROWID)
27 - access(ROWID=ROWID)
31 - access("F"."CONTACTIID"="G"."CONTACTIID")
32 - access("E"."ADDRESSIID"=NVL("D"."BILLINGADDRESSIID","D"."ADDRESSIID"))
------SECOND QUERY
1 - filter("G"."CONTACTIID"=MAX("CONTACTIID"))
13 - access("B"."SITEIID"=300964)
15 - access("B"."PARENTIID"="I"."GROUPIID"(+))
16 - filter("A"."TYPE"=4 AND "A"."INVOICEID" LIKE '%%%')
17 - access("A"."SITEIID"=300964)
19 - access("A"."TERMSIID"="H"."PAYMENTTERMSIID")
21 - access("A"."CREATEDBY"="J"."EMPIID"(+))
23 - access("A"."BILLINGCUSTOMERIID"="D"."CUSTOMERIID")
25 - access("D"."CUSTOMERIID"="CUSTOMERIID")
filter("CUSTOMERIID" IS NOT NULL)
26 - access("E"."ADDRESSIID"=NVL("D"."BILLINGADDRESSIID","D"."ADDRESSIID"))-Avinash

Oracle 9i Performance Issue High Physical Reads

Dear All,
I have Oracle 9i Release 9.2.0.5.0 database under HP Unix, I have run the query and got following output. Can any body just have a look and advise what to do in the following situation? We have performance issues.
Many thanks in advance
Buffer Pool Advisory for DB: DBPR Instance: DBPR End Snap: 902
-> Only rows with estimated physical reads >0 are displayed
Size for Size Buffers for Est Physical Estimated
P Estimate (M) Factr Estimate Read Factor Physical Reads
D 416 .1 51,610 4.27 1,185,670,652
D 832 .2 103,220 2.97 825,437,374
D 1,248 .3 154,830 2.03 563,139,985
D 1,664 .4 206,440 1.49 412,550,232
D 2,080 .5 258,050 1.32 366,745,510
D 2,496 .6 309,660 1.23 340,820,773
D 2,912 .7 361,270 1.14 317,544,771
D 3,328 .8 412,880 1.09 301,680,173
D 3,744 .9 464,490 1.04 288,191,418
D 4,096 1.0 508,160 1.00 276,929,627

Hi,
Actually you didnt give the exact problem statement.
Seems to be your database is I/O bound. Ok, do the following one by one:
1. Identify the FTS queries and try to create the optimal indexes (depending on the disk reads factor!!) on the problem queries.
2. To reduce the 276M physical reads, you need to allocate more memory to db_cache_size. try 8GB (initially) and then depending on the buffer advisery you can increase further if you have more memory on the box.
3. as a Next step , configure KEEP and RECYCLE cache to get the benefits of reduced I/O by multiple pools. Allocate objects to the KEEP/RECYCLE pools.
Thanks,

Hint or parameter to force physical read

I am using Oracle 11.2.0.3. I have a query which took 45 minute the first time and it take 4 minutes in subsequent run in QC environment. In both the cases it uses same plan. If I try the query again in few days , first time it takes considerable amount of time.Most of the wait is in range index scan - 'db file parallel read'
Same query runs within 2 minutes in lower environment with different plan. I have used hint to make the plan same in QC environment. Now query runs as expected but I suspect it might slow down if the data is not cached. I do not have access to alter system flush buffer cache privilege.
Is there any hint or parameter I can use force physical read?
Which view will tell me if a table is still cached in memory?

spur230 wrote:
<snip>
Which view will tell me if a table is still cached in memory?
v$bh will tell you what blocks of an object are cached:
orcla> select file#,block#,status from v$bh where objd=(select data_object_id
2 from dba_objects where owner='SCOTT' and objecT_name='DEPT');
no rows selected
orcla> select * from scott.dept;
    DEPTNO DNAME          LOC
        10 ACCOUNTING     NEW YORK
        20 RESEARCH       DALLAS
        30 SALES          CHICAGO
        40 OPERATIONS     BOSTON
orcla> select file#,block#,status from v$bh where objd=(select data_object_id
2 from dba_objects where owner='SCOTT' and objecT_name='DEPT');
     FILE#     BLOCK# STATUS
         4        131 xcur
         4        134 xcur
         4        132 xcur
         4        135 xcur
         4        130 xcur
         4        133 xcur
6 rows selected.
orcla>
but you do need to be aware of the status. There may be several versions of a block cached.

Physical reads

I 'm running the same query against two databases on two different servers, and not seeing the expected results.
Query runs in 6 seconds on server A, and 32 seconds on server B. The database on B is a copy of the database on A, same blocksize, same db_file_multiblock_read_count.
Query is:
SELECT
IMS_BO_PMAN08.REF_ID,( sum(IMS_BO_PMAN08_TRAN.MONTH_13_APR) ) + ( sum(IMS_BO_PMAN08_TRAN.MONTH_14_MAY) ) ,
decode(IMS_BO_PMAN08_TRAN.TRANS_SUB_TYPE,'A','Actual','F','Forecast'),
decode(IMS_BO_PMAN08_TRAN.TRANS_TYPE,'E','Expenditure','U','Unit completions','A','Allocation Takeup','S','SOS units','T','SOS Expenditure','G','Grant Claim Units','H','Larger Homes','C','FC Unit Completions','F','FC Expenditure','V','ACQ Expenditure')
FROM
IMS_BO_PMAN08,
IMS_BO_PMAN08_TRAN
WHERE
( IMS_BO_PMAN08.PROG_MAN_ID=IMS_BO_PMAN08_TRAN.PROG_MAN_ID )
AND ( IMS_BO_PMAN08.VERSION_ID IN (select version_id from ims_bo_version where version_id = 1 ) )
AND ( IMS_BO_PMAN08.INV_REGION_CODE > 2 )
and decode(IMS_BO_PMAN08_TRAN.TRANS_SUB_TYPE,'A','Actual','F','Forecast') ='Actual'
GROUP BY
IMS_BO_PMAN08.REF_ID,decode(IMS_BO_PMAN08_TRAN.TRANS_SUB_TYPE,'A','Actual','F','Forecast'),
decode(IMS_BO_PMAN08_TRAN.TRANS_TYPE,'E','Expenditure','U','Unit completions','A','Allocation Takeup','S','SOS units','T','SOS Expenditure','G','Grant Claim Units','H','Larger Homes','C','FC Unit Completions','F','FC Expenditure','V','ACQ Expenditure');
I am seeing the same execution plan when running the query against either database, with the same cost in each case. However, the physical reads on server B is ten times that of on server A
Server A
=====
293851 rows selected.
Elapsed: 00:00:06.58
Execution Plan
0 SELECT STATEMENT Optimizer=FIRST_ROWS (Cost=50270 Card=27811 Bytes=973385)
1 0 SORT (GROUP BY) (Cost=50270 Card=27811 Bytes=973385)
2 1 HASH JOIN (Cost=50088 Card=27811 Bytes=973385)
3 2 TABLE ACCESS (BY INDEX ROWID) OF 'IMS_BO_PMAN08' (Cost=17990 Card=26243 Bytes=446131)
4 3 INDEX (RANGE SCAN) OF 'IMS_BO_PMAN08_IX1' (UNIQUE) (Cost=105 Card=26243)
5 2 NESTED LOOPS (Cost=32049 Card=107258 Bytes=1930644)
6 5 INDEX (UNIQUE SCAN) OF 'IMS_BO_VERSION_IX1' (UNIQUE)
7 5 TABLE ACCESS (FULL) OF 'IMS_BO_PMAN08_TRAN' (Cost=32048 Card=107258 Bytes=1716128)
Statistics
0 recursive calls
13 db block gets
288529 consistent gets
*18,218 physical reads*
0 redo size
17924295 bytes sent via SQL*Net to client
2174914 bytes received via SQL*Net from client
19592 SQL*Net roundtrips to/from client
0 sorts (memory)
1 sorts (disk)
293851 rows processed
Server B
=====
292677 rows selected.
Elapsed: 00:00:32.66
Execution Plan
0 SELECT STATEMENT Optimizer=FIRST_ROWS (Cost=50255 Card=27805 Bytes=973175)
1 0 SORT (GROUP BY) (Cost=50255 Card=27805 Bytes=973175)
2 1 HASH JOIN (Cost=50073 Card=27805 Bytes=973175)
3 2 TABLE ACCESS (BY INDEX ROWID) OF 'IMS_BO_PMAN08' (Cost=17984 Card=26237 Bytes=446029)
4 3 INDEX (RANGE SCAN) OF 'IMS_BO_PMAN08_IX1' (UNIQUE) (Cost=105 Card=26237)
5 2 NESTED LOOPS (Cost=32040 Card=107230 Bytes=1930140)
6 5 INDEX (UNIQUE SCAN) OF 'IMS_BO_VERSION_IX1' (UNIQUE)
7 5 TABLE ACCESS (FULL) OF 'IMS_BO_PMAN08_TRAN' (Cost=32039 Card=107230 Bytes=1715680)
Statistics
0 recursive calls
357 db block gets
250918 consistent gets
*188,332 physical reads*
0 redo size
17853447 bytes sent via SQL*Net to client
2166145 bytes received via SQL*Net from client
19513 SQL*Net roundtrips to/from client
0 sorts (memory)
1 sorts (disk)
292677 rows processed
8.1.6.3 on solaris 8
Can anyone tell me where the excessive physical i/o's (and presumably associated runtime) is coming from? Any pointers much appreciated.
Pete
Edited by: user12248598 on 17-Mar-2010 09:01

sort_area_size, sort_area_retained_size & hash_area_size are the same size for both instances, as are all NLS settings.
Tables are not specified NOCACHE, and there are no additional buffer pools.
Running with sql_trace enabled for both queries highlighed some very interesting results:
For the slow query, this is the tkprof output, unfortunately waits=yes is not available in 8.1.6
TKPROF: Release 8.1.6.3.0 - Production on Tue Mar 23 14:54:18 2010
(c) Copyright 1999 Oracle Corporation. All rights reserved.
Trace file: imsroc_ora_10166.trc
Sort options: default
count    = number of times OCI procedure was executed
cpu      = cpu time in seconds executing
elapsed = elapsed time in seconds executing
disk     = number of physical reads of buffers from disk
query    = number of buffers gotten for consistent read
current = number of buffers gotten in current mode (usually for update)
rows     = number of rows processed by the fetch or execute call
alter session set events '10046 trace name context forever, level 8'
call     count       cpu    elapsed       disk      query    current        rows
Parse        0      0.00       0.00          0          0          0           0
Execute      1      0.00       0.00          0          0          0           0
Fetch        0      0.00       0.00          0          0          0           0
total        1      0.00       0.00          0          0          0           0
Misses in library cache during parse: 0
Misses in library cache during execute: 1
Optimizer goal: FIRST_ROWS
Parsing user id: 5
BEGIN DBMS_APPLICATION_INFO.SET_MODULE(:1,NULL); END;
call     count       cpu    elapsed       disk      query    current        rows
Parse        1      0.00       0.00          0          0          0           0
Execute      1      0.01       0.01          0          0          0           1
Fetch        0      0.00       0.00          0          0          0           0
total        2      0.01       0.01          0          0          0           1
Misses in library cache during parse: 1
Optimizer goal: FIRST_ROWS
Parsing user id: 5
SELECT
IMS_BO_PMAN08.REF_ID,
   ( sum(IMS_BO_PMAN08_TRAN.MONTH_13_APR) ) + ( sum(IMS_BO_PMAN08_TRAN.MONTH_14_MAY) ) ,
     decode(IMS_BO_PMAN08_TRAN.TRANS_SUB_TYPE,'A','Actual','F','Forecast'),
decode(IMS_BO_PMAN08_TRAN.TRANS_TYPE,'E','Expenditure','U','Unit completions','A','Allocation Takeup
','S','SOS units','T','SOS Expenditure','G','Grant Claim Units','H','Larger Homes','C','FC Unit Comple
tions','F','FC Expenditure','V','ACQ Expenditure')
FROM
bo_ims.IMS_BO_PMAN08,
bo_ims.IMS_BO_PMAN08_TRAN
WHERE ( IMS_BO_PMAN08.PROG_MAN_ID=IMS_BO_PMAN08_TRAN.PROG_MAN_ID )
AND ( IMS_BO_PMAN08.VERSION_ID IN (select version_id from bo_ims.ims_bo_version where version_id =
1 ) )
    AND ( IMS_BO_PMAN08.INV_REGION_CODE > 2 )
    and decode(IMS_BO_PMAN08_TRAN.TRANS_SUB_TYPE,'A','Actual','F','Forecast') = 'Actual'
GROUP BY
IMS_BO_PMAN08.REF_ID,
    decode(IMS_BO_PMAN08_TRAN.TRANS_SUB_TYPE,'A','Actual','F','Forecast'),
decode(IMS_BO_PMAN08_TRAN.TRANS_TYPE,'E','Expenditure','U','Unit completions','A','Allocation Takeup
','S','SOS units','T','SOS Expenditure','G','Grant Claim Units','H','Larger Homes','C','FC Unit Comple
tions','F','FC Expenditure','V','ACQ Expenditure')
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    16278     15.36      36.39     215625     251560        361      244156
total    16280     15.36      36.39     215625     251560        361      244156
Misses in library cache during parse: 0
Optimizer goal: FIRST_ROWS
Parsing user id: 5
OVERALL TOTALS FOR ALL NON-RECURSIVE STATEMENTS
call     count       cpu    elapsed       disk      query    current        rows
Parse        2      0.00       0.00          0          0          0           0
Execute      3      0.01       0.01          0          0          0           1
Fetch    16278     15.36      36.39     215625     251560        361      244156
total    16283     15.37      36.40     215625     251560        361      244157
Misses in library cache during parse: 1
Misses in library cache during execute: 1
OVERALL TOTALS FOR ALL RECURSIVE STATEMENTS
call     count       cpu    elapsed       disk      query    current        rows
Parse        0      0.00       0.00          0          0          0           0
Execute      0      0.00       0.00          0          0          0           0
Fetch        0      0.00       0.00          0          0          0           0
total        0      0.00       0.00          0          0          0           0
Misses in library cache during parse: 0
    3 user SQL statements in session.
    0 internal SQL statements in session.
    3 SQL statements in session.
Trace file: imsroc_ora_10166.trc
Trace file compatibility: 8.00.04
Sort options: default
       2 sessions in tracefile.
       5 user SQL statements in trace file.
       0 internal SQL statements in trace file.
       3 SQL statements in trace file.
       3 unique SQL statements in trace file.
   75998 lines in trace file.And this is the tkprof formatted output for the faster running query:
TKPROF: Release 8.1.6.3.0 - Production on Tue Mar 23 14:56:28 2010
(c) Copyright 1999 Oracle Corporation. All rights reserved.
Trace file: imslive_ora_7489.trc
Sort options: default
count    = number of times OCI procedure was executed
cpu      = cpu time in seconds executing
elapsed = elapsed time in seconds executing
disk     = number of physical reads of buffers from disk
query    = number of buffers gotten for consistent read
current = number of buffers gotten in current mode (usually for update)
rows     = number of rows processed by the fetch or execute call
alter session set events '10046 trace name context forever, level 8'
call     count       cpu    elapsed       disk      query    current        rows
Parse        0      0.00       0.00          0          0          0           0
Execute      1      0.00       0.00          0          0          0           0
Fetch        0      0.00       0.00          0          0          0           0
total        1      0.00       0.00          0          0          0           0
Misses in library cache during parse: 0
Misses in library cache during execute: 1
Optimizer goal: FIRST_ROWS
Parsing user id: 5
SELECT
IMS_BO_PMAN08.REF_ID,
   ( sum(IMS_BO_PMAN08_TRAN.MONTH_13_APR) ) + ( sum(IMS_BO_PMAN08_TRAN.MONTH_14_MAY) ) ,
     decode(IMS_BO_PMAN08_TRAN.TRANS_SUB_TYPE,:SYS_B_00,:SYS_B_01,:SYS_B_02,:SYS_B_03),
decode(IMS_BO_PMAN08_TRAN.TRANS_TYPE,:SYS_B_04,:SYS_B_05,:SYS_B_06,:SYS_B_07,:SYS_B_08,:SYS_B_09,:SYS_B_10,:
SYS_B_11,:SYS_B_12,:SYS_B_13,:SYS_B_14,:SYS_B_15,:SYS_B_16,:SYS_B_17,:SYS_B_18,:SYS_B_19,:SYS_B_20,:SYS_B_21,:
SYS_B_22,:SYS_B_23)
FROM
BO_IMS.IMS_BO_PMAN08,
BO_IMS.IMS_BO_PMAN08_TRAN
WHERE ( IMS_BO_PMAN08.PROG_MAN_ID=IMS_BO_PMAN08_TRAN.PROG_MAN_ID )
AND ( IMS_BO_PMAN08.VERSION_ID IN (select version_id from bo_ims.ims_bo_version where version_id = :SYS_B_
24 ) )
    AND ( IMS_BO_PMAN08.INV_REGION_CODE > :SYS_B_25 )
    and decode(IMS_BO_PMAN08_TRAN.TRANS_SUB_TYPE,:SYS_B_26,:SYS_B_27,:SYS_B_28,:SYS_B_29) = :SYS_B_30
GROUP BY
IMS_BO_PMAN08.REF_ID,
    decode(IMS_BO_PMAN08_TRAN.TRANS_SUB_TYPE,:SYS_B_31,:SYS_B_32,:SYS_B_33,:SYS_B_34),
decode(IMS_BO_PMAN08_TRAN.TRANS_TYPE,:SYS_B_35,:SYS_B_36,:SYS_B_37,:SYS_B_38,:SYS_B_39,:SYS_B_40,:SYS_B_41,:
SYS_B_42,:SYS_B_43,:SYS_B_44,:SYS_B_45,:SYS_B_46,:SYS_B_47,:SYS_B_48,:SYS_B_49,:SYS_B_50,:SYS_B_51,:SYS_B_52,:
SYS_B_53,:SYS_B_54)
call     count       cpu    elapsed       disk      query    current        rows
Parse        1      0.00       0.00          0          0          0           0
Execute      2      0.00       0.00          0          0          0           0
Fetch    20042      0.00       0.00      20064     295221         13      300608
total    20045      0.00       0.00      20064     295221         13      300608
Misses in library cache during parse: 1
Optimizer goal: FIRST_ROWS
Parsing user id: 5
Rows     Row Source Operation
300608 SORT GROUP BY
300628   NESTED LOOPS
55647    NESTED LOOPS
      2     INDEX UNIQUE SCAN (object id 151050)
55647     TABLE ACCESS BY INDEX ROWID IMS_BO_PMAN08
55649      INDEX RANGE SCAN (object id 185149)
300628    TABLE ACCESS BY INDEX ROWID IMS_BO_PMAN08_TRAN
356274     INDEX RANGE SCAN (object id 157241)
DELETE FROM PLAN_TABLE
WHERE
STATEMENT_ID=:1
call     count       cpu    elapsed       disk      query    current        rows
Parse        1      0.00       0.00          0          0          0           0
Execute      1      0.00       0.00          3          5         12           0
Fetch        0      0.00       0.00          0          0          0           0
total        2      0.00       0.00          3          5         12           0
Misses in library cache during parse: 1
Optimizer goal: FIRST_ROWS
Parsing user id: 5
Rows     Row Source Operation
      1 DELETE PLAN_TABLE
      1   TABLE ACCESS FULL PLAN_TABLE
EXPLAIN PLAN SET STATEMENT_ID='PLUS18028884' FOR SELECT
IMS_BO_PMAN08.REF_ID,
   ( sum(IMS_BO_PMAN08_TRAN.MONTH_13_APR) ) + ( sum(IMS_BO_PMAN08_TRAN.MONTH_14_MAY) ) ,
     decode(IMS_BO_PMAN08_TRAN.TRANS_SUB_TYPE,'A','Actual','F','Forecast'),
decode(IMS_BO_PMAN08_TRAN.TRANS_TYPE,'E','Expenditure','U','Unit completions','A','Allocation Takeup','S','S
OS units','T','SOS Expenditure','G','Grant Claim Units','H','Larger Homes','C','FC Unit Completions','F','FC E
xpenditure','V','ACQ Expenditure')
FROM
BO_IMS.IMS_BO_PMAN08,
BO_IMS.IMS_BO_PMAN08_TRAN
WHERE ( IMS_BO_PMAN08.PROG_MAN_ID=IMS_BO_PMAN08_TRAN.PROG_MAN_ID )
AND ( IMS_BO_PMAN08.VERSION_ID IN (select version_id from bo_ims.ims_bo_version where version_id = 1 ) )
    AND ( IMS_BO_PMAN08.INV_REGION_CODE > 2 )
    and decode(IMS_BO_PMAN08_TRAN.TRANS_SUB_TYPE,'A','Actual','F','Forecast') = 'Actual'
GROUP BY
IMS_BO_PMAN08.REF_ID,
    decode(IMS_BO_PMAN08_TRAN.TRANS_SUB_TYPE,'A','Actual','F','Forecast'),
decode(IMS_BO_PMAN08_TRAN.TRANS_TYPE,'E','Expenditure','U','Unit completions','A','Allocation Takeup','S','S
OS units','T','SOS Expenditure','G','Grant Claim Units','H','Larger Homes','C','FC Unit Completions','F','FC E
xpenditure','V','ACQ Expenditure')
call     count       cpu    elapsed       disk      query    current        rows
Parse        1      0.00       0.00          0          0          0           0
Execute      0      0.00       0.00          0          0          0           0
Fetch        0      0.00       0.00          0          0          0           0
total        1      0.00       0.00          0          0          0           0
Misses in library cache during parse: 1
Optimizer goal: FIRST_ROWS
Parsing user id: 5
insert into plan_table (statement_id, timestamp, operation, options,
object_node, object_owner, object_name, object_instance, object_type,
search_columns, id, parent_id, position, other,optimizer, cost, cardinality,
   bytes, other_tag, partition_start, partition_stop, partition_id,
distribution )
values
(:1,SYSDATE,:2,:3,:4,:5,:6,:7,:8,:9,:10,:11,:12,:13,:14,:15,:16,:17,:18,:19,
:20,:21,:22)
call     count       cpu    elapsed       disk      query    current        rows
Parse        1      0.00       0.00          0          0          0           0
Execute      7      0.00       0.00          1          3          9           7
Fetch        0      0.00       0.00          0          0          0           0
total        8      0.00       0.00          1          3          9           7
Misses in library cache during parse: 1
Optimizer goal: FIRST_ROWS
Parsing user id: 5     (recursive depth: 1)
select o.name, u.name
from
sys.obj$ o, sys.user$ u where obj# = :1and owner# = user#
call     count       cpu    elapsed       disk      query    current        rows
Parse        1      0.00       0.00          0          0          0           0
Execute      2      0.00       0.00          0          0          0           0
Fetch        2      0.00       0.00          3         12          0           2
total        5      0.00       0.00          3         12          0           2
Misses in library cache during parse: 1
Optimizer goal: CHOOSE
Parsing user id: SYS   (recursive depth: 1)
OVERALL TOTALS FOR ALL NON-RECURSIVE STATEMENTS
call     count       cpu    elapsed       disk      query    current        rows
Parse        3      0.00       0.00          0          0          0           0
Execute      4      0.00       0.00          3          5         12           0
Fetch    20042      0.00       0.00      20064     295221         13      300608
total    20049      0.00       0.00      20067     295226         25      300608
Misses in library cache during parse: 3
Misses in library cache during execute: 1
OVERALL TOTALS FOR ALL RECURSIVE STATEMENTS
call     count       cpu    elapsed       disk      query    current        rows
Parse        2      0.00       0.00          0          0          0           0
Execute      9      0.00       0.00          1          3          9           7
Fetch        2      0.00       0.00          3         12          0           2
total       13      0.00       0.00          4         15          9           9
Misses in library cache during parse: 2
    5 user SQL statements in session.
    1 internal SQL statements in session.
    6 SQL statements in session.
Trace file: imslive_ora_7489.trc
Trace file compatibility: 8.00.04
Sort options: default
       3 sessions in tracefile.
       8 user SQL statements in trace file.
       1 internal SQL statements in trace file.
       6 SQL statements in trace file.
       6 unique SQL statements in trace file.
   77410 lines in trace file.The sql statement as run did not make use of bind variables, so the ones in the tkprof output for the longer running statement made me immediately think of cursor sharing, and right there in the init.ora for the faster running database was CURSOR_SHARING=FORCE.
I'm not familiar with the history of the databases, nor the specific reasoning for enabling cursor sharing (bind variable usage seems prevalent in all custom code) so I've replicated the setting on the slower database, resulting in a similar tkprof output to the faster server, with a runtime of 7 seconds for 2nd and subsequent runs.
My immediate issue is now solved, thanks to all who contributed, and apologies for not spotting the obvious earlier.
Regards, Pete

Logical reads VS physical reads

hello all,
What is the difference between logical reads and physical read ??? I do get the part of logical read (from buffer) and physical read(from disk). And also do know physical reads are bad, but is it true in oracle world..logical reads are bad ??? if so why ??? Could you please explain which on to look for. As i am going thru AWR report and i see segemts by logical/physical read.

The first and foremost difference is that physcial reads are done from the hard disk. And this is always going tobe slwoer than the memory. That's why its said that the physcial ios must be removed. Logical ios are good as they are done from the memory.The theory that logical are also not good is because the logical ios require the access given by latches. So with lots of the gets for the latches put them in to contention and latch contention would make the access to the logical io slower.So its better to do this in less IO even they are logical too.
Lots of logical IOs probably mean that you are accessing unnecessary data which may be not required.
HTH
Aman....

Understanding Physical Reads

Similar Messages

Maybe you are looking for