Re: Having both dbwr_io_slaves and disk_asynch_io set

  • From: Tim Gorman <tim@xxxxxxxxx>
  • To: "'Oracle-L (E-mail)" <oracle-l@xxxxxxxxxxxxx>
  • Date: Thu, 23 Dec 2004 21:46:43 -0700


DBWR_IO_SLAVES is a really poor attempt at asynch I/O, and it has dozens of
bugs against it from v8.0.x through v9.2.0x.  Don't take my word for it --
search MetaLink on the parameter name as keyword, be sure to click on
"Advanced Search" and "Bug Database".  It is a bottleneck to performance
besides.  Don't use it.

If you feel you need more bandwidth on your DBWR, then please consider
setting DB_WRITER_PROCESSES > 1 -- setting it no higher than CPU_COUNT seems
to work OK.

Hope this helps...


on 12/6/04 8:21 PM, Richard Ji at richard.c.ji@xxxxxxxxx wrote:

> I found out on a database (8174, Solaris 8 Sparc, EMC) that I use,
> while disk_asynch_io is set to true, the dbwr_io_slaves is set to non zero, 6.
> And I am seeing a lot of "slave wait" events.  The two obviously conflicts and
> I wonder what kind of effect this have caused when both are enabled.
> Thanks.
> --


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