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RE: DBWR, Direct I/O and the Devil

From: Bobak, Mark <Mark.Bobak_at_il.proquest.com>
Date: Wed, 28 Nov 2007 16:07:40 -0500
Message-ID: <AA29A27627F842409E1D18FB19CDCF270E22EBE3@AABO-EXCHANGE02.bos.il.pqe>


Don,

I think you want both direct *and* async I/O configured, if your O/S and filesystem will support it. In that case (with async i/o) you probably will only need 1 DBWR. In addition to what Kevin has written in his blog, Steve Adams has some good stuff on his website: http://www.ixora.com.au/tips/avoid_buffered_io.htm http://www.ixora.com.au/tips/use_asynchronous_io.htm

And there are several others at:
http://www.ixora.com.au/tips/

It's old, but still relevant, I think.

-Mark

--
Mark J. Bobak
Senior Database Administrator, System & Product Technologies
ProQuest
789 E. Eisenhower, Parkway, P.O. Box 1346
Ann Arbor MI 48106-1346
+1.734.997.4059  or +1.800.521.0600 x 4059
mark.bobak_at_il.proquest.com
www.proquest.com
www.csa.com

ProQuest...Start here. 


-----Original Message-----
From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Don Seiler
Sent: Wednesday, November 28, 2007 2:39 PM
To: Taylor, Chris David
Cc: Oracle-L Freelists
Subject: Re: DBWR, Direct I/O and the Devil

On Nov 28, 2007 1:32 PM, Taylor, Chris David
<Chris.Taylor_at_ingrambarge.com> wrote:

> Do you believe you have an I/O issue or are you just trying to "squeeze"
> more out of your I/O subsystem?
Right now I just want to know that I don't have some horribly obvious (to everyone else) misconfiguration. Obviously having a stable setup is paramount, I'll worry about tuning again after that. With my recent rash of performance issues, I'm going through any and all configuration changes that I made in the past 3 months and questioning everything.
> Having played with db_writer_processes, I haven't really seen much
> improvement or negative impact from increasing/decreasing them. But
> that is probably more due to the load (or lack thereof to notice any
> difference).
As I said, I'm all in favor of dropping down to 1, maybe back up to 2 if need be. I just wanted to know if there's any concerns to be aware of with the number of DBWR processes in direct vs. asynch I/O. -- Don Seiler http://seilerwerks.wordpress.com ultimate: http://www.mufc.us -- http://www.freelists.org/webpage/oracle-l -- http://www.freelists.org/webpage/oracle-l
Received on Wed Nov 28 2007 - 15:07:40 CST

Original text of this message

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