RE: DBWR, Direct I/O and the Devil

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

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ProQuest
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-----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
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