Full table scans and EUL

Hi All,
I am using Discoverer Version 10.1.2.1.
I have few reports in which tables used in queries (used in Custom folders) go into full table scans inspite of all efforts in tuning.
I came to know that full table scans also come from the way EUL is built and maintained.
Can anyone please throw some light on how does EUL and full table scan relate.
Also one more thing here, which is better to use, Database View on which we can base our folder or writing the complete complex query in the folder.
Any help in this case will be appreciated.
Regards,
Ankur

Hi,
Can anyone please throw some light on how does EUL and full table scan relateThe database cost base optimiser processes the SQL that has been generated by Discoverer and creates an execution plan for the SQL. Now the execution plan will contain full table scans if the CBO calculates that FTS will give the best results. The CBO mainly uses the statistics held against the tables and the conditions in the SQL to calculate whether FTS would be better than using an index. The table join conditions are usually defined in the EUL but other conditions are usually in the workbook.
So there are many factors which control whether the database uses an FTS and only a few of them are affected by how the EUL is built.
Database View on which we can base our folder or writing the complete complex query in the folderIn general, it is always better to create a database view if that option is available to you. You can control and monitor the SQL in a database view much more easily than using a query in a custom folder.
Rod West

Similar Messages

Update doing full table scan and taking long time

Hi All,
I am running an update statement which is doing a full table scan.
UPDATE Database.TABLE AS T
SET COMMENTS = CAST(CAST(COALESCE(T.COMMENTS,0) AS INTEGER) + 1 AS
CHARACTER)
WHERE T.TRACKINGPOINT = 'NDEL'
AND T.REFERENCENUMBER =
SUBSTRING(Root.XML.EE_EAI_MESSAGE.ReferenceNumber || '
' FROM 1 FOR 32);
Any advice.
Regards,
Umair

Mustafa,
No Developer is writing it in his program.
Regards,
Umair

Full table scan and how to avoid it

Hello,
I have two tables, one with 425,000 records, and the other with 5,200,000 records in it. The smaller table has an index on its unique primary key, and the bigger table has an index on the foreign key of the smaller table.
When joining these two tables, I keep getting full table scans on both of these tables, and I would like to understand the philosophy behind it as well as ways to avoid this.
Thanks

Are you manipulating the join columns in any fashion? Such as applying a function to them like in
to_char(column_a) = to_char(column_b)Because any manipulation like that will obviate your index (assuming you don't have function based indexes).
Really though, without your tables, indexes and query, we're left with voodoo, which is cool, but not really that effective.
*note to any and all practicing witch doctors, i really do think voodoo is cool and effective, please don't persecute me for my speakings.
Message was edited by:
Tubby

Question about Full Table Scans and Tablespaces

Good evening (or morning),
I'm reading the Oracle Concepts (I'm new to Oracle) and it seems that, based on the way that Oracle allocates and manages storage the following premise would be true:
Premise: A table that is often accessed using a full table scan (for whatever reasons) would best reside in its own dedicated tablespace.
The main reason I came to this conclusion is that when doing a full table scan, Oracle does multiblock I/O, likely reading one extent at a time. If the Tablespace's datafile(s) only contain data for a single table then a serial read will not have to skip over segments that contain data for other tables (as would be the case if the tablespace is shared with other tables). The performance improvement is probably small but, it would seem that there is one nonetheless.
I'd like to have the thoughts of experienced DBAs regarding the above premise.
Thank you for your contribution,
John.

Good morning :) Aman,
>
A little correction! A segment(be it a table,index, cluster, temporary) , would stay always in its own tablespace. Segments can't span tablespaces!
>
Fortunately, I understood that from the beginning :)
You mentioned fragmentation, I understand that too. As rows get deleted small holes start existing in the segment and those holes are not easily reusable because of their limited size.
What I am referring to is different though.
Let's consider a tablespace that is the home of 2 or more tables, the tablespace in turn is represented by one or more OS datafiles, in that case the situation will be as shown in the following diagram (not a very good diagram but... best I can do here ;) ):
Tablespace TablespaceWithManyTables
(segment 1 contents)
    TableA Extent 1
      TableA Block 1
      TableA Block 2
      Fragmentation may happen in these blocks or
      even across blocks because Oracle allows rows
      to span blocks
      TableA Block n
    End of TableA Extent 1
    more extents here all for TableA
(end of segment 1 contents)
(segment 2 contents)
    TableZ Extent 5
      blocks here
    End of TableZ Extent 5
    more extents here, all for tableZ
(end of segment 2 contents)
    and so on
(more segments belonging to various tables)
end of Tablespace TablespaceWithManyTablesOn the other hand, if the tablespace hosts only one table, the layout will be:
Tablespace TablespaceExclusiveForTableA
(segment 1 contents)
    TableA Extent 1
      TableA Block 1
      TableA Block 2
      Fragmentation may happen in these blocks or
      even across blocks because Oracle allows rows
      to span blocks
      TableA Block n
    End of TableA Extent 1
    another extent for TableA
(end of segment 1 contents)
(segment 2 contents)
    TableA Extent 5
      blocks here
    End of TableA Extent 5
    more extents for TableA
(end of segment 2 contents)
and so on
(more segments belonging to TableA)
end of Tablespace TablespaceExclusiveForTableAThe fragmentation you mentioned takes place in both cases. In the first case, regardless of fragmentation, some segments don't belong to the table that is being serially scanned, therefore they have to be skipped over at the OS level. In the second case, since all the extents belong to the same table, they can be read serially at the OS level. I realize that in that case the segments may not be read in the "right" sequence but they don't have to because they can be served to the client app in sequence.
It is because of this that, I thought that if a particular table is mostly read serially, there might be a performance benefit (and also less work for Oracle) to dedicate a tablespace to it.
I can't wait to see what you think of this :)
John.

Full Table Scans and LRU

Hello,
In a full table scan I understand that the memory block used for a newly read table block is placed at the end of the LRU.
When the second table block is read, is the same memory block replaced?
What I am asking basically is whether for a full table scan only one block in the data buffer is ever used, with the same single block being recycled for the entire content of the table.
Kind regards,
Peter Strauss

Hi Fidel,
> In oracle 10g it changes a little the behavior. It is
> recommended not to set MULTIBLOCK_READ_COUNT. You
> calculate system statistics and Oracle "decides" the
> best value.
Take care... oracle 10gR2 uses the system statistic values to calculate the costs (= execution plan) including the i/o statistics but for the multiple i/o it uses the parameter DB_FILE_MULTIBLOCK_READ_COUNT.
So the result is: For calculating it uses the system statistic and for the work itself it uses DB_FILE_MULTIBLOCK_READ_COUNT (if set).
http://jonathanlewis.wordpress.com/2007/05/20/system-stats-strategy/
For the LRU thing ... oracle has a nice explanation:
http://download.oracle.com/docs/cd/B19306_01/server.102/b14220/memory.htm
Regards
Stefan

How to avoid this full table scan (and index FFS) ?

Hi All,
Oracle 11.2 on Linux.
See this query and its plan below
SQL> DELETE
2 FROM TABLEA APE
3 WHERE NOT EXISTS
4 (SELECT 1
5 FROM TABLEB AP
6 WHERE AP.col1 = APE.col1
7 AND AP.col2 = APE.col2
8 AND AP.col3 = APE.col3)
9 AND ROWNUM < 51 ;
50 rows deleted.
Elapsed: 00:12:01.07
Execution Plan
Plan hash value: 1740911877
| Id | Operation | Name | Rows | Bytes |TempSpc| Cost (%CPU)| Time |
| 0 | DELETE STATEMENT | | 50 | 2650 | | 573K (1)| 01:54:40 |
| 1 | DELETE | TABLEA | | | | | |
|* 2 | COUNT STOPKEY | | | | | | |
|* 3 | HASH JOIN RIGHT ANTI | | 80M| 4059M| 1775M| 573K (1)| 01:54:40 |
| 4 | INDEX FAST FULL SCAN| TABLEB_UK | 47M| 1228M| | 96480 (1)| 00:19:18 |
| 5 | TABLE ACCESS FULL | TABLEA | 80M| 1991M| | 243K (1)| 00:48:42 |
---------------------------------------------------------------------------------------------------------In both tables, TABLEA and TABLEB, there is index on columns col1-col2-col3 as leading columns (TABLEB has few more columns in the index, but after these 3 columns).
Requirement is, I want to delete first 50 records in TABLEA, which does not exist in TABLEB.
I tried with various hints, but Oracle is always doing a full scan on one of the tables and index FFS on other. In some cases, Oracle did full scan on both tables and then deleted 50 records. Stats is up-to-date. Doing a full scan on tables with 80 million and 47 million rows is a bit too much for deleting 50 rows.
How I can make Oracle do
1) Read TABLEA row-by-row
2) for each row, check if it exists in TABLEB
3) If not exists, then delete row from TABLEA, else continue
4) Stop reading TABLEA after we have deleted 50 records
Thanks in advance

>
>
Oracle 11.2 on Linux.
SQL> DELETE
2 FROM TABLEA APE
3 WHERE NOT EXISTS
4 (SELECT 1
5 FROM TABLEB AP
6 WHERE AP.col1 = APE.col1
7 AND AP.col2 = APE.col2
8 AND AP.col3 = APE.col3)
9 AND ROWNUM < 51 ;
50 rows deleted.
Elapsed: 00:12:01.07
Execution Plan
Plan hash value: 1740911877
| Id | Operation | Name | Rows | Bytes |TempSpc| Cost (%CPU)| Time |
| 0 | DELETE STATEMENT | | 50 | 2650 | | 573K (1)| 01:54:40 |
| 1 | DELETE | TABLEA | | | | | |
|* 2 | COUNT STOPKEY | | | | | | |
|* 3 | HASH JOIN RIGHT ANTI | | 80M| 4059M| 1775M| 573K (1)| 01:54:40 |
| 4 | INDEX FAST FULL SCAN| TABLEB_UK | 47M| 1228M| | 96480 (1)| 00:19:18 |
| 5 | TABLE ACCESS FULL | TABLEA | 80M| 1991M| | 243K (1)| 00:48:42 |
---------------------------------------------------------------------------------------------------------Requirement is, I want to delete first 50 records in TABLEA, which does not exist in TABLEB.
Such requirements usually make me curious - what's special about a randomly selected 50 rows ?
Is this trying to delete the data in batches of 50 rows at a time.
How I can make Oracle do
1) Read TABLEA row-by-row
2) for each row, check if it exists in TABLEB
3) If not exists, then delete row from TABLEA, else continue
4) Stop reading TABLEA after we have deleted 50 records
It look's as if a 'no_unnest' hint in the subquery should do what you want. It should make Oracle run the quey with a FILTER subquery. You could then choose to drive the delete through a tablescan of tableA or an index range scan of the index on tableA. Have you considered the effect of (and requirements relating to) nulls in the three columns of either table ?
Regards
Jonathan Lewis
http://jonathanlewis.wordpress.com
Author: Oracle Core

Tables in subquery resulting in full table scans

Hi,
This is related to a p1 bug 13009447. Customer recently upgraded to 10G. Customer reported this type of problem for the second time.
Problem Description:
All the tables in sub-query are resulting in full table scans and hence are executing for hours.
Here is the query
SELECT /*+ PARALLEL*/
act.assignment_action_id
, act.assignment_id
, act.tax_unit_id
, as1.person_id
, as1.effective_start_date
, as1.primary_flag
FROM pay_payroll_actions pa1
, pay_population_ranges pop
, per_periods_of_service pos
, per_all_assignments_f as1
, pay_assignment_actions act
, pay_payroll_actions pa2
, pay_action_classifications pcl
, per_all_assignments_f as2
WHERE pa1.payroll_action_id = :b2
AND pa2.payroll_id = pa1.payroll_id
AND pa2.effective_date
BETWEEN pa1.start_date
AND pa1.effective_date
AND act.payroll_action_id = pa2.payroll_action_id
AND act.action_status IN ('C', 'S')
AND pcl.classification_name = :b3
AND pa2.consolidation_set_id = pa1.consolidation_set_id
AND pa2.action_type = pcl.action_type
AND nvl (pa2.future_process_mode, 'Y') = 'Y'
AND as1.assignment_id = act.assignment_id
AND pa1.effective_date
BETWEEN as1.effective_start_date
AND as1.effective_end_date
AND as2.assignment_id = act.assignment_id
AND pa2.effective_date
BETWEEN as2.effective_start_date
AND as2.effective_end_date
AND as2.payroll_id = as1.payroll_id
AND pos.period_of_service_id = as1.period_of_service_id
AND pop.payroll_action_id = :b2
AND pop.chunk_number = :b1
AND pos.person_id = pop.person_id
AND (
as1.payroll_id = pa1.payroll_id
OR pa1.payroll_id IS NULL
AND NOT EXISTS
SELECT /*+ PARALLEL*/ NULL
FROM pay_assignment_actions ac2
, pay_payroll_actions pa3
, pay_action_interlocks int
WHERE int.locked_action_id = act.assignment_action_id
AND ac2.assignment_action_id = int.locking_action_id
AND pa3.payroll_action_id = ac2.payroll_action_id
AND pa3.action_type IN ('P', 'U')
AND NOT EXISTS
SELECT /*+ PARALLEL*/
NULL
FROM per_all_assignments_f as3
, pay_assignment_actions ac3
WHERE :b4 = 'N'
AND ac3.payroll_action_id = pa2.payroll_action_id
AND ac3.action_status NOT IN ('C', 'S')
AND as3.assignment_id = ac3.assignment_id
AND pa2.effective_date
BETWEEN as3.effective_start_date
AND as3.effective_end_date
AND as3.person_id = as2.person_id
ORDER BY as1.person_id
, as1.primary_flag DESC
, as1.effective_start_date
, act.assignment_id
FOR UPDATE OF as1.assignment_id
, pos.period_of_service_id
Here is the execution plan for this query. We tried adding hints in sub-query to force indexes to pick-up but it is still doing Full table scans.
Suspecting some db parameter which is causing this issue.
In the
- Full table scans on tables in the first sub-query
PAY_PAYROLL_ACTIONS, PAY_ASSIGNMENT_ACTIONS, PAY_ACTION_INTERLOCKS
- Full table scans on tables in Second sub-query
PER_ALL_ASSIGNMENTS_F PAY_ASSIGNMENT_ACTIONS
call count cpu elapsed disk query current rows
Parse 1 0.00 0.00 0 0 0 0
Execute 29 398.80 2192.99 238706 4991924 2383 0
Fetch 1136 378.38 1921.39 0 4820511 0 1108
total 1166 777.19 4114.38 238706 9812435 2383 1108
Misses in library cache during parse: 1
Misses in library cache during execute: 1
Optimizer mode: ALL_ROWS
Parsing user id: 41 (APPS) (recursive depth: 1)
Rows Execution Plan
0 SELECT STATEMENT MODE: ALL_ROWS
0 FOR UPDATE
0 PX COORDINATOR
0 PX SEND (QC (ORDER)) OF ':TQ10009' [:Q1009]
0 SORT (ORDER BY) [:Q1009]
0 PX RECEIVE [:Q1009]
0 PX SEND (RANGE) OF ':TQ10008' [:Q1008]
0 HASH JOIN (ANTI BUFFERED) [:Q1008]
0 PX RECEIVE [:Q1008]
0 PX SEND (HASH) OF ':TQ10006' [:Q1006]
0 BUFFER (SORT) [:Q1006]
0 TABLE ACCESS MODE: ANALYZED (BY INDEX ROWID) OF 'PER_ALL_ASSIGNMENTS_F' (TABLE) [:Q1006]
0 NESTED LOOPS [:Q1006]
0 NESTED LOOPS [:Q1006]
0 NESTED LOOPS [:Q1006]
0 HASH JOIN (ANTI) [:Q1006]
0 BUFFER (SORT) [:Q1006]
0 PX RECEIVE [:Q1006]
0 PX SEND (HASH) OF ':TQ10002'
0 TABLE ACCESS MODE: ANALYZED (BY INDEX ROWID) OF 'PAY_ASSIGNMENT_ACTIONS' (TABLE)
0 NESTED LOOPS
0 NESTED LOOPS
0 NESTED LOOPS
0 NESTED LOOPS
0 TABLE ACCESS MODE: ANALYZED (BY INDEX ROWID) OF 'PAY_PAYROLL_ACTIONS' (TABLE)
0 INDEX MODE: ANALYZED (UNIQUE SCAN) OF 'PAY_PAYROLL_ACTIONS_PK' (INDEX (UNIQUE)
0 INDEX MODE: ANALYZED (RANGE SCAN) OF 'PAY_POPULATION_RANGES_N4' (INDEX)
0 TABLE ACCESS MODE: ANALYZED (BY INDEX ROWID) OF 'PER_PERIODS_OF_SERVICE' (TABLE)
0 INDEX MODE: ANALYZED (RANGE SCAN) OF 'PER_PERIODS_OF_SERVICE_N3' (INDEX)
0 TABLE ACCESS MODE: ANALYZED (BY INDEX ROWID) OF 'PER_ALL_ASSIGNMENTS_F' (TABLE)
0 INDEX MODE: ANALYZED (RANGE SCAN) OF 'PER_ASSIGNMENTS_N4' (INDEX)
0 INDEX MODE: ANALYZED (RANGE SCAN) OF 'PAY_ASSIGNMENT_ACTIONS_N51' (INDEX)
0 PX RECEIVE [:Q1006]
0 PX SEND (HASH) OF ':TQ10005' [:Q1005]
0 VIEW OF 'VW_SQ_1' (VIEW) [:Q1005]
0 HASH JOIN [:Q1005]
0 BUFFER (SORT) [:Q1005]
0 PX RECEIVE [:Q1005]
0 PX SEND (BROADCAST) OF ':TQ10000'
0 TABLE ACCESS MODE: ANALYZED (FULL) OF 'PAY_PAYROLL_ACTIONS' (TABLE)
0 HASH JOIN [:Q1005]
0 PX RECEIVE [:Q1005]
0 PX SEND (HASH) OF ':TQ10004' [:Q1004]
0 PX BLOCK (ITERATOR) [:Q1004]
0 TABLE ACCESS MODE: ANALYZED (FULL) OF 'PAY_ASSIGNMENT_ACTIONS' (TABLE) [:Q1004]
0 BUFFER (SORT) [:Q1005]
0 PX RECEIVE [:Q1005]
0 PX SEND (HASH) OF ':TQ10001'
0 TABLE ACCESS MODE: ANALYZED (FULL) OF 'PAY_ACTION_INTERLOCKS' (TABLE)
0 TABLE ACCESS MODE: ANALYZED (BY INDEX ROWID) OF 'PAY_PAYROLL_ACTIONS' (TABLE) [:Q1006]
0 INDEX MODE: ANALYZED (UNIQUE SCAN) OF 'PAY_PAYROLL_ACTIONS_PK' (INDEX (UNIQUE)) [:Q1006]
0 INDEX MODE: ANALYZED (UNIQUE SCAN) OF 'PAY_ACTION_CLASSIFICATIONS_PK' (INDEX (UNIQUE))[:Q1006]
0 INDEX MODE: ANALYZED (RANGE SCAN) OF 'PER_ASSIGNMENTS_F_PK' (INDEX (UNIQUE)) [:Q1006]
0 PX RECEIVE [:Q1008]
0 PX SEND (HASH) OF ':TQ10007' [:Q1007]
0 VIEW OF 'VW_SQ_2' (VIEW) [:Q1007]
0 FILTER [:Q1007]
0 HASH JOIN [:Q1007]
0 BUFFER (SORT) [:Q1007]
0 PX RECEIVE [:Q1007]
0 PX SEND (BROADCAST) OF ':TQ10003'
0 TABLE ACCESS MODE: ANALYZED (FULL) OF 'PER_ALL_ASSIGNMENTS_F' (TABLE)
0 PX BLOCK (ITERATOR) [:Q1007]
0 TABLE ACCESS MODE: ANALYZED (FULL) OF 'PAY_ASSIGNMENT_ACTIONS' (TABLE) [:Q1007]
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
enq: KO - fast object checkpoint 32 0.02 0.12
os thread startup 8 0.02 0.19
PX Deq: Join ACK 198 0.00 0.04
PX Deq Credit: send blkd 167116 1.95 1103.72
PX Deq Credit: need buffer 327389 1.95 266.30
PX Deq: Parse Reply 148 0.01 0.03
PX Deq: Execute Reply 11531 1.95 1901.50
PX qref latch 23060 0.00 0.60
db file sequential read 108199 0.17 22.11
db file scattered read 9272 0.19 51.74
PX Deq: Table Q qref 78 0.00 0.03
PX Deq: Signal ACK 1165 0.10 10.84
enq: PS - contention 73 0.00 0.00
reliable message 27 0.00 0.00
latch free 218 0.00 0.01
latch: session allocation 11 0.00 0.00
Thanks in advance
Suresh PV

Hi,
welcome,
how is the query performing if you delete all the hints for PARALLEL, because most of the waits are related to waits on Parallel.
Herald ten Dam
http://htendam.wordpress.com
PS. Use "{code}" for showing your code and explain plans, it looks nicer

Does Table Statistics collection have any effect on Full Table scan

We are using SQL Parallelism in Oracle 10g 10.2.0.4 (3 node RAC ).Most of the the big tables are going for FTS.
And these Table are truncated and loaded inside procedures and then used in next procedures in SELECT query.
As there is no stats or stale STATS available , does this affect the FTS performance.

Well, typically, it's a good idea to have up to date stats on your tables, so that the Optimiser has an idea what data is in the tables and can determine if an index or a full table scan is the best method of access. It doesn't necessarily remove full table scans, and a FTS is not necessarily a bad thing, but having up to date stats let's the optimiser choose what's best, based on the data, rather than making a wrong decision.

Star Query Full Table Scan

Hi, Folks:
I have a complex SQL statement that runs very slowly.
Following is the statement:
SELECT
T3.POSITION_ID,
T12.PR_POSTN_ID,
T12.PR_TERR_ID,
T12.PR_REP_MANL_FLG,
T9.CREATED,
T10.PR_EMP_ID,
T9.MODIFICATION_NUM,
T12.DEDUP_TOKEN,
T12.LOCATION_LEVEL,
T12.PR_PRTNR_OU_ID,
T12.PR_OU_TYPE_ID,
T12.PAR_DUNS_NUM,
T3.ACCNT_NAME,
T11.ATTRIB_16,
T6.PAR_ROW_ID,
T3.INVSTR_FLG,
T6.ROW_ID,
T12.DUNS_NUM,
T12.BU_ID,
T10.ROW_ID,
T2.LAST_NAME,
T3.SRV_PROVDR_FLG,
T12.X_PR_MERCH_NBR_ID,
T3.ROW_STATUS,
T12.NAME,
T11.PAR_ROW_ID,
T6.LAST_UPD_BY,
T6.MODIFICATION_NUM,
T3.PRIORITY_FLG,
T10.NAME,
T3.ASGN_SYS_FLG,
T9.PROFIT,
T12.PR_BL_ADDR_ID,
T12.PR_REP_ASGN_TYPE,
T9.LAST_UPD_BY,
T3.FACILITY_FLG,
T12.LAST_UPD_BY,
T12.PR_SHIP_ADDR_ID,
T11.MODIFICATION_NUM,
T11.LAST_UPD_BY,
T5.LOGIN,
T3.ASGN_MANL_FLG
FROM
S_ADDR_ORG T1,
S_CONTACT T2,
S_ACCNT_POSTN T3,
S_ORG_INT T4,
S_EMPLOYEE T5,
S_ORG_EXT_FNX T6,
S_ORG_SYN T7,
S_INDUST T8,
S_ORG_EXT_T T9,
S_POSTN T10,
S_ORG_EXT_X T11,
S_ORG_EXT T12
WHERE
T12.BU_ID = T4.ROW_ID (+) AND
T12.PR_CON_ID = T2.ROW_ID (+) AND
T12.ROW_ID = T7.OU_ID AND
T12.ROW_ID = T11.PAR_ROW_ID (+) AND
T12.ROW_ID = T6.PAR_ROW_ID (+) AND
T12.ROW_ID = T9.PAR_ROW_ID (+) AND
T12.PR_INDUST_ID = T8.ROW_ID (+) AND
T12.PR_ADDR_ID = T1.ROW_ID (+) AND
T12.PR_POSTN_ID = T10.ROW_ID AND
T12.PR_POSTN_ID = T3.POSITION_ID AND
T12.ROW_ID = T3.OU_EXT_ID AND
T10.PR_EMP_ID = T5.ROW_ID (+) AND
(T12.X_BMO_CUST_FLG = 'Y') AND
(T7.NAME IS NULL );
***** SQL Statement Execute Time: 31.703 seconds *****
I do a explain plan and found the table S_ORG_EXT (T12)
get a full table scan.
But I found the table S_ORG_EXT did have lots of indexes
build on each column shown in the where statement.
Our database use RULE base optimizer and it should use
index instead of full table scan.
Then, I look at this SQL and realize it is a star query.
One more thing is that the table S_ORG_SYN (T7) defined
the column NAME as NOT NULL. If the query process, it
should return no row.
But I still don't know for what reason the Oracle use
full table scan and ignore the S_ORG_SYN.NAME should be
NOT NULL
If I want to avoid the full table scan, how can I do by
not switching to COST base optimizer mode ?
Thanks,
Ke

Michael:
A nice explanantion. In my experience, in versions up to 8.1.7, the RBO seems to be faster in the large majority of queries than the CBO. In our payroll application (version 8.0.5), removing statistics cut the time for the calculation run from 6.5 hours to under 2.
The CBO seems to be significantly faster in 9i. We only have one application currently running in a 9.0.1 database. In this app, a large stored procedure took about 2 minutes to run when there were no statistics, and about 10 seconds after we analyzed the tables.
As more of our vendors migrate to 9 (we just got the last vendor migrated off 7.3 to 8.0.6 a couple of months ago), I may become a bigger fan of the CBO. John,
I remember having a discussion with you about the CBO in a thread once and am aware of your opinion of the CBO. My opinion has been test which works for you RBO or CBO - in our case we verified that CBO worked better for us. Anyway, I was searching metalink and it looks like you'll be forced to become a "bigger fan" of the CBO after 9i release 2. This is from part of Doc ID 189702.1 on metalink:
The rule-based optimizer (RBO) will be no longer be a valid optimization choice when Oracle9i is de-supported. The release after Oracle9i
(referred to in this article as Oracle10i) will only support the cost-based optimizer (CBO). Hence Oracle9i Release 2 is the last releases to
contain the RBO. Partners and customers should certify their applications with the CBO before that time.
...but of course Oracle has been warning people of the demise of the RBO for some time.
Al

Avod full table scan help...

HI ,
I have sql with some filter and all the have index. the table size is huge index is there in explain plan though index it's going for full table scan it's not recognizing index. i used index hint/*+ INDEX (SYM.SYM_DEPL,SYM.SYDB_DE_N18) */ though it's not recoginizing index in explian plan going for full table scan. and qury take more time.
please help to resolve the issue and it should recognize index rather than full table scan..

user13301356 wrote:
HI ,
I have sql with some filter and all the have index. the table size is huge index is there in explain plan though index it's going for full table scan it's not recognizing index. i used index hint/*+ INDEX (SYM.SYM_DEPL,SYM.SYDB_DE_N18) */ though it's not recoginizing index in explian plan going for full table scan. and qury take more time.
please help to resolve the issue and it should recognize index rather than full table scan..What is database version? Are all columns in the table indexed? Copy and paste the query that you are executing.

Full Table Scan issue

Hi,
I have a two tables (TAB1, TAB2)
I wrote a SQL query on these two tables and included other tables..
Col1 & Col2 in TAB1 defined as Char(8)
Col1 & Col2 in TAB2 defined as VarChar(8)
in the query where clause I wrote like
TAB2.Col1 = TRIM(TAB1.Col1)
and TAB2.Col1 = TRIM(TAB1.Col2)
Problem: If I add TRIM(), it is doing a full table scan and query is very very slow..
How to fix this issue?
Thanks

Sorry, I am not giving full details here.. but here is some info..
(11) TABLE ACCESS FULL TAB1 [Analyzed]
(11) Blocks: 430 Est. Rows: 62,770 of 62,770 Cost: 67
(19) TABLE ACCESS FULL STAT_ONE [Analyzed]
(19) Blocks: 821 Est. Rows: 53,580 of 53,580 Cost: 63
Index? U mean on COL1 & COL2? no idea I will find out..
Thanks

Slow queries and full table scans in spite of context index

I have defined a USER_DATASTORE, which uses a PL/SQL procedure to compile data from several tables. The master table has 1.3 million rows, and one of the fields being joined is a CLOB field.
The resulting token table has 65,000 rows, which seems about right.
If I query the token table for a word, such as "ORACLE" in the token_text field, I see that the token_count is 139. This query returns instantly.
The query against the master table is very slow, taking about 15 minutes to return the 139 rows.
Example query:
select hnd from master_table where contains(myindex,'ORACLE',1) > 0;
I've run a sql_trace on this query, and it shows full table scans on both the master table and the DR$MYINDEX$I table. Why is it doing this, and how can I fix it?

After looking at the tuning FAQ, I can see that this is doing a functional lookup instead of an indexed lookup. But why, when the rows are not constrained by any structural query, and how can I get it to instead to an indexed lookup?
Thanks in advance,
Annie

Slow query due to large table and full table scan

Hi,
We have a large Oracle database, v 10g. Two of the tables in the database have over one million rows.
We have a few queries which take a lot of time to execute. Not always though, it that seems when load is high the queries tend
to take much longer. Average time may be 1 or 2 seconds, but maxtime can be up to 2 minutes.
We have now used Oracle Grid to help us examine the queries. We have found that some of the queries require two or three full table scans.
Two of the full table scans are of the two large tables mentioned above.
This is an example query:
SELECT table1.column, table2.column, table3.column
FROM table1
JOIN table2 on table1.table2Id = table2.id
LEFT JOIN table3 on table2.table3id = table3.id
WHERE table1.id IN(
SELECT id
FROM (
(SELECT a.*, rownum rnum FROM(
SELECT table1.id
FROM table1,
table2,
table3
WHERE
table1.table2id = table2.id
AND
table2.table3id IS NULL OR table2.table3id = :table3IdParameter
) a
WHERE rownum <= :end))
WHERE rnum >= :start
Table1 and table2 are the large tables in this example. This query starts two full table scans on those tables.
Can we avoid this? We have, what we think are, the correct indexes.
/best regards, Håkan

>
Hi Håkan - welcome to the forum.
We have a large Oracle database, v 10g. Two of the tables in the database have over one million rows.
We have a few queries which take a lot of time to execute. Not always though, it that seems when load is high the queries tend
to take much longer. Average time may be 1 or 2 seconds, but maxtime can be up to 2 minutes.
We have now used Oracle Grid to help us examine the queries. We have found that some of the queries require two or three full table scans.
Two of the full table scans are of the two large tables mentioned above.
This is an example query:Firstly, please read the forum FAQ - top right of page.
Please format your SQL using tags [code /code].
In order to help us to help you.
Please post table structures - relevant (i.e. joined, FK, PK fields only) in the form - note use of code tags - we can just run table create script.
CREATE TABLE table1
Field1 Type1,
Field2 Type2,
FieldN TypeN
);Then give us some table data - not 100's of records - just enough in the form
INSERT INTO Table1 VALUES(Field1, Field2.... FieldN);
..Please post EXPLAIN PLAN - again with tags.
HTH,
Paul...
/best regards, Håkan

"db file scattered read" too high and Query going for full table scan-Why ?

Hi,
I had a big table of around 200mb and had a index on it.
In my query I am using the where clause which has to use the
index. I am neither using any not null condition
nor using any function on the index fields.
Still my query is not using the index.
It is going for full table scan.
Also the statspack report is showing the
"db file scattered read" too high.
Can any body help and suggest me why this is happenning.
Also tell me the possible solution for it.
Thanks
Arun Tayal

"db file scattered read" are physical reads/multi block reads. This wait occurs when the session reading data blocks from disk and writing into the memory.
Take the execution plan of the query and see what is wrong and why the index is not being used.
However, FTS are not always bad. By the way, what is your db_block_size and db_file_multiblock_read_count values?
If those values are set to high, Optimizer always favour FTS thinking that reading multiblock is always faster than single reads (index scans).
Dont see oracle not using index, just find out why oracle is not using index. Use the INDEX hint to force optimizer to use index. Take the execution with/witout index and compare the cardinality,cost and of course, logical reads.
Jaffar
Message was edited by:
The Human Fly

Select statement in a function does Full Table Scan

All,
I have been coding a stored procedure that writes 38K rows in less than a minute. If I add another column which requires call to a package and 4 functions within that package, it runs for about 4 hours. I have confirmed that due to problems in one of the functions, the code does full table scans. The package and all of its functions were written by other contractors who have been long gone.
Please note that case_number_in (VARCHAR2) and effective_date_in (DATE) are parameters sent to the problem function and I have verified through TOAD’s debugger that their values are correct.
Table named ps2_benefit_register has over 40 million rows but case_number is an index for that table.
Table named ps1_case_fs has more than 20 million rows but also uses case_number as an index.
Select #1 – causes full table scan runs and writes 38K rows in a couple of hours.
{case}
SELECT max(a2.application_date)
INTO l_app_date
FROM dwfssd.ps2_benefit_register a1, dwfssd.ps2_case_fs a2
WHERE a2.case_number = case_number_in and
a1.case_number = a2.case_number and
a2.application_date <= effective_date_in and
a1.DOCUMENT_TYPE = 'F';
{case}
Select #2 – runs – hard coding values makes the code to write the same 38K rows in a few minutes.
{case}
SELECT max(a2.application_date)
INTO l_app_date
FROM dwfssd.ps2_benefit_register a1, dwfssd.ps2_case_fs a2
WHERE a2.case_number = 'A006438' and
a1.case_number = a2.case_number and
a2.application_date <= '01-Apr-2009' and
a1.DOCUMENT_TYPE = 'F';
{case}
Why using the values in the passed parameter in the first select statement causes full table scan?
Thank you for your help,
Seyed
Edited by: user11117178 on Jul 30, 2009 6:22 AM
Edited by: user11117178 on Jul 30, 2009 6:23 AM
Edited by: user11117178 on Jul 30, 2009 6:24 AM

Hello Dan,
Thank you for your input. The function is not determinsitic, therefore, I am providing you with the explain plan. By version number, if you are refering to the Database version, we are running 10g.
PLAN_TABLE_OUTPUT
Plan hash value: 2132048964
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | Pstart| Pstop |
| 0 | SELECT STATEMENT | | 324K| 33M| 3138 (5)| 00:00:38 | | |
|* 1 | HASH JOIN | | 324K| 33M| 3138 (5)| 00:00:38 | | |
| 2 | BITMAP CONVERSION TO ROWIDS | | 3 | 9 | 1 (0)| 00:00:01 | | |
|* 3 | BITMAP INDEX FAST FULL SCAN| IDX_PS2_ACTION_TYPES | | | | | | |
| 4 | PARTITION RANGE ITERATOR | | 866K| 87M| 3121 (4)| 00:00:38 | 154 | 158 |
| 5 | TABLE ACCESS FULL | PS2_FS_TRANSACTION_FACT | 866K| 87M| 3121 (4)| 00:00:38 | 154 | 158 |
Predicate Information (identified by operation id):
 1 - access("AL1"."ACTION_TYPE_ID"="AL2"."ACTION_TYPE_ID")
 3 - filter("AL2"."ACTION_TYPE"='1' OR "AL2"."ACTION_TYPE"='2' OR "AL2"."ACTION_TYPE"='S')
Thank you very much,
Seyed

Full table scans and EUL

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