Thomas:
I think you are right on monitoring the db writer performance. You
should look the write complete waits/ free buffer waits to understand
the db writer contention. I am not sure what prompted your Sr.DBA to
think on increasing the IO slaves or db writers.
KG
- Thomas Jeff <jeff.thomas_at_thomson.net> wrote:
> Running 9.2.0.2 on AIX 4.3.3. We recently experienced a situation
> where
> a datawarehouse database crashed due to a bug dealing with
> DBWR_IO_SLAVES > 0.
> Oracle's recommended fix was to set the DBWR_IO_SLAVES to 0, which I
> did.
>
> Now, my understanding is that if AIO is enabled on the box, the rule
> of
> thumb
> appears to be to use DB_WRITER_PROCESSES and set DBWR_IO_SLAVES = 0.
>
> Now, the Sr DBA here is screaming about the performance since I made
> the
> change,
> in particular, he says he's seeing high redo latch contention and
> redo
> log
> buffer waits which he says validates his contention that we need to
> get
> back to
> using DBWR_IO_SLAVES.
>
> I admit I'm confused. I don't clearly see the relationship that he
> complaining
> about.
>
> My idea of 'monitoring' was to assess free buffer waits, and to
> monitor
> the batch
> schedules to see if any degradation in timing had occurred, and since
> the change,
> neither has been an issue.
>
> Am I missing something? What stats should I be assessing to
> contrast
> the
> use of DB_WRITER_PROCESSES vs DBWR_IO_SLAVES? And yes, I've googled
> and
> metalinked and and most information is mainly pertinent to 7.3.4 and
> 8i
> and of
> a more general nature.
>
> And yes, DISK_ASCYCH_IO is set to TRUE.
>
> Thanks.
>
> --------------------------------------------
> Jeffery D Thomas
> DBA
> Thomson Information Services
> Thomson, Inc.
>
> Email: jeff.thomas_at_thomson.net
>
> Indy DBA Master Documentation available at:
> http://gkmqp.tce.com/tis_dba
> --------------------------------------------
>
>
>
Have a nice day !!
Best Regards,
K Gopalakrishnan,
Bangalore, INDIA.
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Received on Fri Jan 09 2004 - 13:39:27 CST