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RE: DB file sequential reads

From: Yasin Baskan <>
Date: Thu, 4 Oct 2007 16:35:40 +0300
Message-ID: <083667B535F3464CA0DD0D1DAFA4E3760E9B389B@camexc1.kfs.local>

Starting with 9.2 you get a section named "row source operation" for each sql in a tkprof output. This section gives numbers for consistent reads, disk reads, writes and timing for each step in the execution plan. By looking at the number of reads here you can find out which index they are on.

10G provides these as default. In 9.2 you need to set statistics_level=ALL for these numbers. Otherwise you see the row source operations but not their statistics. The following is on 9.2 (t is a copy of all_objects with an index on object_name). See also Metalink note 295656.1 titled "Row Source Operation Statistics in SQL_TRACE Files".

SQL> alter session set statistics_level=all;

Session altered.

SQL> alter session set events '10046 trace name context forever, level 12';

Session altered.

SQL> select * from t where object_name='STANDARD';

select *
 t where object_name='STANDARD'

call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ----------

Parse 1 0.01 0.00 0 0 0 0
Execute 1 0.00 0.00 0 0 0 0
Fetch 2 0.00 0.00 2 5 0 2
------- ------ -------- ---------- ---------- ---------- ----------

total 4 0.01 0.00 2 5 0 2

Misses in library cache during parse: 1
Optimizer goal: CHOOSE
Parsing user id: 113

Rows Row Source Operation
------- ---------------------------------------------------

      2  TABLE ACCESS BY INDEX ROWID T (cr=5 r=2 w=0 time=820 us)
      2   INDEX RANGE SCAN T1IND (cr=3 r=1 w=0 time=588 us)(object id

-----Original Message-----

[] On Behalf Of Hameed, Amir Sent: Thursday, October 04, 2007 3:29 PM To: oracle-l
Subject: DB file sequential reads

In a 10046 trace file taken at level 12, is there a way to find out which index is experiencing most of the sequential reads?



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-- Received on Thu Oct 04 2007 - 08:35:40 CDT

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