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RE: Need help tuning FTS

From: <Yosi_at_comhill.com>
Date: Wed, 06 Jun 2001 12:02:12 -0700
Message-ID: <F001.0031EE66.20010606114728@fatcity.com>

Wild guess, way out of left field, is there a sequence in the select statement, that might have a high cache value in QA, but a low cache value in prod?

> -----Original Message-----
> From: Srini.Chavali_at_Cummins.com [mailto:Srini.Chavali_at_Cummins.com]
> Sent: Wednesday, June 06, 2001 2:47 PM
> To: Multiple recipients of list ORACLE-L
> Subject: Need help tuning FTS
>
>
> All,
> I need some help in tuning a select statement that performs a
> FTS. (The FTS
> is deliberate !) It takes over 5 hours to run in our prod
> instance, but
> takes less than 10 min in our QA instance. The QA instance
> was copied from
> prod about 6 weeks ago and is identical to prod, except for
> db_block_buffers whose value is 20000 in prod and 15000 in QA. The
> instances run on identical hardware (Compaq TRU 64, 8 Gig RAM
> & 8 cpus).
> The table in question has 3 million rows in prod and 2.8
> million rows in
> QA. Explain plans are identical. DB version in both is
> 8.1.6.0 and both are
> using RBO.
>
> While running in prod, I took a level 12 trace and here is a
> snippet form
> the trace file -
>
> WAIT #1: nam='latch free' ela= 2 p1=17190174328 p2=66 p3=0
> WAIT #1: nam='latch free' ela= 2 p1=17190304728 p2=66 p3=0
> WAIT #1: nam='latch free' ela= 2 p1=17189692728 p2=66 p3=0
> WAIT #1: nam='dbfile scattered read' ela= 1 p1=12 p2=266267 p3=16
> WAIT #1: nam='latch free' ela=2 p1=17189819928 p2=66 p3=0
> WAIT #1: nam='latch free' ela= 27 p1=17190272728 p2=66 p3=0
> WAIT #1: nam='db file scattered read' ela= 0 p1=12 p2=266269 p3=15
> WAIT #1: nam='latch free' ela= 3 p1=17189935928 p2=66 p3=0
> WAIT #1: nam='latch free' ela= 2 p1=17189917528 p2=66 p3=0
> WAIT #1: nam='db file scattered read' ela= 5 p1=12 p2=266804 p3=16
> WAIT #1: nam='db file scattered read' ela= 1 p1=12 p2=266820 p3=16
> WAIT #1: nam='db file scattered read' ela= 1 p1=12 p2=266836 p3=16
> WAIT #1: nam='db file scattered read' ela= 4 p1=12 p2=266852 p3=16
> WAIT #1: nam='db file scattered read' ela= 1 p1=12 p2=266868 p3=16
> WAIT #1: nam='latch free' ela= 5 p1=17190273528 p2=66 p3=0
> WAIT #1: nam='latch free' ela= 2 p1=17190310328 p2=66 p3=0
> WAIT #1: nam='latch free' ela=1 p1=17189831128 p2=66 p3=0
> WAIT #1: nam='latch free' ela= 2 p1=17189801528 p2=66 p3=0
> WAIT #1: nam='latch free' ela= 2 p1=17189801528 p2=66 p3=0
> WAIT #1: nam='latch free' ela= 3 p1=17190166328 p2=66 p3=0
> WAIT #1: nam='db file scattered read' ela= 1 p1=12 p2=266884 p3=16
> WAIT #1: nam='db file scattered read' ela= 3 p1=12 p2=266900 p3=16
> WAIT #1: nam='latch free' ela= 2 p1=17190259928 p2=66 p3=0
>
> I see a lot of time is spent in waiting for latch #66 (cache
> buffer chains) - Metalink states that this could be because
> of a *very* hot block being
> accessed frequently,
> further snooping (via x$bh) shows that there is no such contention.
>
> Can anybody help ?
>
> Thanks much !
> Srini Chavali
> Oracle DBA
> Cummins Inc
>
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.com
> --
> Author:
> INET: Srini.Chavali_at_Cummins.com
>
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-- 
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-- 
Author: 
  INET: Yosi_at_comhill.com

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Received on Wed Jun 06 2001 - 14:02:12 CDT

Original text of this message

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