RE: High buffer gets
- From: "Hameed, Amir" <Amir.Hameed@xxxxxxxxx>
- To: "John Clarke" <john.clarke@xxxxxxxxxxxx>, <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 3 Feb 2012 12:26:26 -0500
We run statistics on schemas as shown below:
- Once a week on ALL schemas
- Daily on the custom schema
On this particular table, gather statistic was run on 30-JAN-2012 and
the job ran longer on 31-JAN-2012 and 01-FEB-2012. The explain plan for
this statement is:
Rows Row Source Operation
------- ---------------------------------------------------
1 FOR UPDATE (cr7248 pr#51 pw=0 time=0 us)
2 SORT ORDER BY (cr7248 pr#51 pw=0 time=0 us cost=9 size!6
card=2)
1 CONCATENATION (cr7248 pr#51 pw=0 time=0 us)
0 FILTER (cr=0 pr=0 pw=0 time=0 us)
0 TABLE ACCESS BY INDEX ROWID MTL_ONHAND_QUANTITIES_DETAIL
(cr=0 pr=0 pw=0 time=0 us cost=4 size8 card=1)
0 INDEX RANGE SCAN MTL_ONHAND_QUANTITIES_N5 (cr=0 pr=0 pw=0
time=0 us cost=3 size=0 card=1)(object id 402327)
1 FILTER (cr7248 pr#51 pw=0 time=0 us)
1 TABLE ACCESS BY INDEX ROWID MTL_ONHAND_QUANTITIES_DETAIL
(cr7248 pr#51 pw=0 time=0 us cost=4 size8 card=1)
203798 INDEX RANGE SCAN MTL_ONHAND_QUANTITIES_N5 (cr00 pr=0
pw=0 time=0 us cost=3 size=0 card=1)(object id 402327)
Amir
From: John Clarke [mailto:john.clarke@xxxxxxxxxxxx]
Sent: Friday, February 03, 2012 12:21 PM
To: Hameed, Amir; oracle-l@xxxxxxxxxxxxx
Subject: Re: High buffer gets
Without seeing any SQL statements or execution plans, I'd probably guess
it's statistics-related (i.e., they're out-of-date, missing, etc).
Difficult to say though without seeing more of the trace file.
- John
From: "Hameed, Amir" <Amir.Hameed@xxxxxxxxx>
Reply-To: "Amir.Hameed@xxxxxxxxx" <Amir.Hameed@xxxxxxxxx>
Date: Fri, 3 Feb 2012 11:31:46 -0500
To: "oracle-l@xxxxxxxxxxxxx" <oracle-l@xxxxxxxxxxxxx>
Subject: High buffer gets
Folks,
We have an Oracle ERP system (11.5.10) with database version 11.1.0.7
running on Solaris 9. There are batch jobs, submitted via concurrent
managers, that have been running fine for a long time. About two weeks
ago, we went through a release cycle where new code and functionality
was introduced into this environment and since then some of the critical
jobs that have been running fine are now running longer most of the
times. We have taken traces of jobs and the one thing that is common to
all of them is the sheer number of buffer gets from consistent reads. I
am pasting statistics from one such job below. This is from a standard
Oracle code. The obj# from the raw trace file showed an INVENTORY table
that is updated heavily by the application in general. An interesting
observation is that this particular job runs fine on days when the
inventory table is not heavily updated concurrently by the other jobs,
introduced by the new code, that run when this job runs longer. But this
behavior is not just limited to this job as there are other critical
jobs that have also started to show the same behavior all of a sudden.
call count cpu elapsed disk query current
rows
------- ------ -------- ---------- ---------- ---------- ----------
----------
Parse 1 0.00 0.00 0 0 0
0
Execute 7811 8711.44 8501.30 14964 294967869 97122
0
Fetch 7811 0.61 0.61 0 0 0
49048
------- ------ -------- ---------- ---------- ---------- ----------
----------
total 15623 8712.05 8501.92 14964 294967869 97122
49048
Has anyone seen this type of behavior? We are going to open an SR with
Oracle to see if we are hitting some type of bug here. Any feedback will
be appreciated.
Thanks
Amir
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