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Home -> Community -> Mailing Lists -> Oracle-L -> RE: Issue with Parallel query execution
Just to wrap up this discussion thread, this is what I found.
Oracle determines the parallel degree depending on the number of rows in the table debtmanagernewaccountc1. I have set the parallel degree of this table from 1 to 4. It now runs in parallel mode all the time. The query uses the materialized subquery using WITH clause of 9i. I have reduced the average runtime by 50%.
WITH dmnewaccountnorslrc1 AS
(
SELECT dm1.marketcd, dm1.acctnodenbr
FROM debtmanagernewaccountc1 dm1
WHERE NOT EXISTS (
SELECT 1
FROM customer cu
WHERE dm1.acctnodenbr = cu.nodenbr
AND cu.custtypecd = 'RS'))
SELECT dm.marketcd, dm.acctnodenbr, ol1.nodenbr, ol1.ordernbr,
ol1.orderlinenbr, ol1.orderlinetypecd, ol1.startts, oh1.closets,
NVL (msc.mobilechgresncd, ' '), NVL (msc.switchxactstatuscd, ' ')
FROM dmnewaccountnorslrc1 dm,
orderline ol1,
orderheader oh1,
mobilestatuschange msc
WHERE ( (dm.acctnodenbr > ' ' AND dm.marketcd = ' ')
OR dm.acctnodenbr >= ' '
)
AND dm.acctnodenbr = oh1.acctnodenbr
AND oh1.ordernbr = ol1.ordernbr
AND oh1.marketcd = ol1.marketcd
AND ol1.startts <= TO_DATE ('20070109200224', 'YYYYMMDDHH24MISS')
AND oh1.closets <= TO_DATE ('20070109200224', 'YYYYMMDDHH24MISS')
AND oh1.closets > TO_DATE ('20050109200224', 'YYYYMMDDHH24MISS')
AND oh1.orderstatuscd = 'C'
AND ol1.ordernbr = msc.ordernbr(+)
AND ol1.orderlinenbr = msc.orderlinenbr(+)
UNION
ol1.orderlinenbr, ol1.orderlinetypecd, ol1.startts, oh1.closets,
' ' AS mobilechgresncd, ' ' AS switchxactstatuscd
FROM dmnewaccountnorslrc1 dm,
accounthistory ah,
orderline ol1,
orderheader oh1
WHERE ( (dm.acctnodenbr > ' ' AND dm.marketcd = ' ')
OR dm.acctnodenbr >= ' '
)
AND dm.marketcd = ah.marketcd
AND dm.acctnodenbr = ah.parentnodenbr
AND ah.effectivets <= '20070109200224'
AND ah.effectivets > '20050109200224'
AND ah.nodenbr = ol1.nodenbr
AND oh1.ordernbr = ol1.ordernbr
AND oh1.marketcd = ol1.marketcd
AND ol1.startts <= TO_DATE ('20070109200224', 'YYYYMMDDHH24MISS')
AND oh1.closets <= TO_DATE ('20070109200224', 'YYYYMMDDHH24MISS')
AND oh1.closets > TO_DATE ('20050109200224', 'YYYYMMDDHH24MISS')
AND oh1.orderstatuscd = 'C'
-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org]On Behalf Of Arumugam, Govind
Sent: Tuesday, December 12, 2006 3:13 PM
To: oracle-l_at_freelists.org
Subject: Issue with Parallel query execution
Dear Gurus,
I am troubleshooting one of the daily batch programs that is not requesting the right amount of parallel degree. I see this job requesting a parallel degree of 4 and getting 4. But in yesterday's run, it only asked for 2 and got 2. The degree of parallelism is set at the table level. We are on "Oracle9i Enterprise Edition Release 9.2.0.6.0 - 64bit Production"
The job started at 21:16 and completed at 22:47, a runtime of 91 minutes running with a degree of 2. It typically runs in less than 40 minutes if it runs with a degree of 4.
I went through the metalink note Checklist for Performance Problems with Parallel Execution Note:280939.1. The data from v$px_session is saved off to a file every 5 minutes using the query "select * from v$px_session"
Date Time v$sysstat Parameter Name Value 12112006 21:10 Parallel operations not downgraded 15727655 12112006 21:10 Parallel operations downgraded to serial 17048 12112006 21:10 Parallel operations downgraded 25 to 50 pct 1162 12112006 21:10 Parallel operations downgraded 1 to 25 pct 583 12112006 21:15 Parallel operations not downgraded 15729888 12112006 21:15 Parallel operations downgraded to serial 17048 12112006 21:15 Parallel operations downgraded 25 to 50 pct 1162 12112006 21:15 Parallel operations downgraded 1 to 25 pct 583
The job started around here. We had a plenty of parallel server threads available for Oracle to use as seen by "select * from V$PQ_SYSSTAT". We used up just 72 out of a maximum of 281 parallel threads.
STATISTIC VALUE ------------------------------ ---------- Servers Busy 72 Servers Idle 20 Servers Highwater 281 12112006 21:20 Parallel operations not downgraded 15732051 12112006 21:20 Parallel operations downgraded to serial 17052 12112006 21:20 Parallel operations downgraded 25 to 50 pct 1162 12112006 21:20 Parallel operations downgraded 1 to 25 pct 583 12112006 21:25 Parallel operations not downgraded 15733831 12112006 21:25 Parallel operations downgraded to serial 17052 12112006 21:25 Parallel operations downgraded 25 to 50 pct 1162 12112006 21:25 Parallel operations downgraded 1 to 25 pct 583 SID SERIAL# PSID USERNAME PROCESS Command STAT PROGRAM Physical Rds ------ ------- ------ --------- ------------ ------------------ ---- ------------------------------ ------------ 528 53832 1332 PVXDBE3A 5856 SELECT ACTI oracle_at_acilf510 (P034) 0 1332 34009 1332 PVXDBE3A 25735 ACTI ? @acilh508 (TNS V1-V3) 4,204 1890 49106 1332 PVXDBE3A 5866 SELECT ACTI oracle_at_acilf510 (P037) 13,947 1529 16639 1332 PVXDBE3A 5862 SELECT ACTI oracle_at_acilf510 (P035) 0 2360 24030 1332 PVXDBE3A 5864 SELECT ACTI oracle_at_acilf510 (P036) 14,019 SADDR SID SERIAL# QCSID QCSERIAL# QCINST_ID SERVER_GROUP SERVER_SET SERVER# DEGREE REQ_DEGREE ---------------- ------ ------- ---------- ---------- ---------- ------------ ---------- ---------- ---------- ---------- 0000040240A4D0E8 528 53832 1332 34009 1 1 1 1 2 2 0000040241AC5F10 1332 34009 1332 000004023FAC6F98 1529 16639 1332 34009 1 1 1 2 2 2 0000040243B3DAF8 2360 24030 1332 34009 1 1 2 1 2 2 0000040243AFFA18 1890 49106 1332 34009 1 1 2 2 2 2
Is there a way for us to find out why the DOP was chosen at 2 for this query?
I would greatly appreciate any insight. I am thinking about "alter SESSION FORCE PARALLEL QUERY PARALLEL 4" through a logon trigger to force the DOP at 4 as a workaround. This will be tested in a production like environment first. Any other solutions or pointers?
Sorry about the long e-mail.
Thanks,
Govind
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