Re: Delete Performance Issue

Hi Don

One of the things you could try is parallel DML if your database server is not too cpu bound.

Plus, verify that relevant indices are present.

HTH
-Rajeev

On 12/21/06, Don Doo <doodon_at_gmail.com> wrote:
>
> Hi,
>
> We are facing a serious performance
> issue. This is a delete statement and
> it takes 4 hours to delete 2.3 million
> rows from a 65 million row table.
> The c_trace table has only one index
> (the primary key) The table is not
> partitioned (we don't have the budget
> to pay for partition option) Other tables
> have less than 5000 rows.
> The sub-query returns 3 to 6 rows
> depending on the values
>
> Query
>
> delete from c_trace
> where targetperiod= 200612
> and RUNSEQ in (select
> RunSeq from C_Run pr,
> C_Summary ss,
> C_Stage st
> where pr.RunSeq = ss.RunSeq
> and ss.stageType = st.stageType
> and st.name = 'load'
> and pr.period = 361
> and ss.Active = 'yes')
>
>
> The V$session_longops shows
>
> 1 select OPNAME||' '||MESSAGE||' '||ELAPSED_SECONDS from
> v$session_longops
> 2* where sql_hash_value=2467621466
> SQL> /
> OPNAME||''||MESSAGE||''||ELA
> ----------------------------------------------------------------------------------------
>
> Hash Join Hash Join: : 6592 out of 6592 Blocks done 13688
> Hash Join Hash Join: : 6272 out of 6272 Blocks done 12753
> Hash Join Hash Join: : 6272 out of 6272 Blocks done 13594
> Hash Join Hash Join: : 7488 out of 7488 Blocks done 14050
>
> Looks like it takes 14050 seconds to complete the hash join which
> matches the time taken to complete the delete.
>
> select HASH_VALUE,CPU_TIME,elapsed_time/(1000000*60),
> fetches,disk_reads,
> BUFFER_GETS,ROWS_PROCESsed
> from v$sql where hash_value = 2467621466
>
> HASH_VALUE CPU_TIME FETCHES DISK_READS BUFFER_GETS ROWS_PROCESSED
> ---------- ---------- ------------------------- ---------- ----------
> ----------- --------------
> 2467621466 193010000 0 1265770
> 13820713 2325397
> Oracle version 9.2.0.4
> Hash_area_size 8 MB
> Sort_area_size 4 MB
> Statistics are current..
> We are using ASSM for these tables.
> I would really appreciate any ideas to improve this statement. We cannot
> do a event trace
> here until mid of January next year because we are behind the SLA and
> don't want to make it slower.
>
> Regards,
>
> Don
>

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