Re: Are db_writer_processes and disk_asynch_io mutually exclusive on Solaris ? Thanks, rm.

From: Ranko Mosic <ranko.mosic_at_gmail.com>
Date: Sat, 10 Sep 2005 09:07:32 -0400
Message-ID: <367369f1050910060761412a26@mail.gmail.com>

Quote from metalink:

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From: Oracle, Frank Marshall 13-Nov-03 21:38 Subject: Re : dbwn VS asy io

You can not use multiple DBWR's with asynch IO. You turn off asynch_io and use multiple db writers ( up to 10) or you use asynch_io and one DBWR. It is an either or situation.

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Also metalink note Note:97291.1 says:
If the application is not very write intensive (or even a DSS system) and async I/O is available, then consider a single DBWR writer process;

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More, there was a bug on Solaris in the past: when both db_writer_processes and disk_asynch_io were enabled performance suffered.

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rm

On 9/9/05, Mladen Gogala <gogala_at_sbcglobal.net> wrote:
>
>
> On 09/09/2005 09:41:37 PM, Lou Fangxin wrote:
> > We hit some problem on solaris with multiple db writer, and finnaly set
> it
> > to one, then the database run well.
>
> I'm running with 3 DBWR processes, for more then a year, with async I/O.
> Slowaris 9,
> Oracle 9.2.0.5 <http://9.2.0.5>, RAC. My users are storing documents into
> the database as BLOB's and
> that is very write-intensive, so I need multiple writers - 1 per I/O
> controller.
> No problems. The only thing that is incompatible with async I/O are I/O
> slaves, which
> are intended to simulate async I/O. That is explained in the note 97291.1.
> However, on HP-UX it is not recommended to use multiple DBWR processes and
> async I/O.
> This is an old information, from the time that I was working for OXHP,
> which used to
> have 4-way OPS (not RAC) system. I remember oracle support guy telling me
> that it is
> not advised to use that combo on HP-UX 11.0. It was a brand new system, we
> finished
> transition from an old Siemens Reliant Unix to HP-UX on Sunday,
> 09/09/2001. Tomorrow,
> on Monday 09/10/2001 I was very busy solving various problems, but
> everything was successful
> in the end. I thought that I will relax a bit as of the day after. The day
> after was, of
> course, Tuesday 9/11/2001 and the world as I knew it ended that day.
>
> --
> Mladen Gogala
> http://www.mgogala.com
>
>
>

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Received on Sat Sep 10 2005 - 08:09:36 CDT