Re: DB file sequential reads
- From: "Vlad Sadilovskiy" <vlovsky@xxxxxxxxx>
- To: yasin.baskan@xxxxxxxxxxxxxxxx
- Date: Thu, 4 Oct 2007 18:37:58 -0400
You can count and map sequential reads from the raw trace to objects in the
DB. p1 parameter represents file# and p2 block#. Be aware that both "db file
scattered read" and "db file sequential read" contribute to the physical
reads count in the row sourse operation statistics. Hence, you'd need to
separate operations that employs "db file sequential reads" from the rest. I
think there are no operations that use both, but I can be mistaken.
Vlad Sadilovskiy
Oracle Database Tools
http://www.fourthelephant.com
On 10/4/07, Yasin Baskan <yasin.baskan@xxxxxxxxxxxxxxxx> wrote:
>
>
>
> 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 *
> from
> 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
> 161667)
>
>
> -----Original Message-----
> From: oracle-l-bounce@xxxxxxxxxxxxx
> [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Hameed, Amir
> Sent: Thursday, October 04, 2007 3:29 PM
> To: oracle-l
> Subject: DB file sequential reads
>
> Folks,
> 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?
>
> Thanks
> Amir
>
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