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Re: Tuning File IO on 8.0.5 and a Netapp file system

From: Casey Dyke <>
Date: Fri, 31 Aug 2001 00:47:28 -0700
Message-ID: <>

Hi Kevin,

This comes straight from a Netapp Engineers response to me about a similar question:

Easy one... our doc's say:

DBWR = 2 * number of CPUS you have in server.

I guess dbwr in this case (I never pursued it) could be either db_writer_processes or dbwr_io_slaves. Assuming you actually need a bit more dbwr grunt, it's probably best to play with the settings and see what combination gives you the best throughput. IO slaves theoretically incur more overhead due to their master/slave relationship w/the db writer process whereas db writer processes work on their own and (so my reading states) should be set = db_lru_latches. Would seem a bit odd to set db_writer_processes to > the number of cpus, so I'm not entirely sure of the merit to that statement. Also, setting either of these parameters (they are mutually exclusive) will have extra cpu/memory cost and what not. YMMV and I would certainly be interested to hear how you go. You know disk_asynch_io should be set to false if you're connecting to a filer, nasty errors could occur otherwise ... :-)

HTH, Cheers,

Casey ...

On Thu, 30 Aug 2001, Kevin Lange wrote:

> I am trying to figure out how to configure the DBWR_IO_SLAVES parameter on
> our system. We are running 8.0.5 and are using Network Appliances as our
> file storage.
> For those who do not know Network Appliances, they have a file system called
> the WAFL (Wrate Anywhere) file layout. This means that you really do not
> configure individual drives or mount points based on individual physical
> drives. The OS takes care of placing the data where it wants to. Its
> prety quick and is working out well for Oracle. But, since there are no
> specific drives to count up, how do you come up with a reasonable
> DBWR_IO_SLAVES value on this system ??
> Thanks
> Kevin

Please see the official ORACLE-L FAQ:
Author: Casey Dyke

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Received on Fri Aug 31 2001 - 02:47:28 CDT

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