Re: Having both dbwr_io_slaves and disk_asynch_io set

Jared,

As far as I understand it. On Solaris 8 and onward, by default Asynch IO is turned on and Oracle will use it by issue a KAIO. If it's raw device or Veritas quick IO, the KAIO will succeed. Otherwise KAIO will fail and an AIO that's simulated by LWP doing pwrite() will happen. That's why there are 258 LWP under the DBWR process.

Now, I can turn Asynch IO off and use Oracle's dbwr slaves to simulate that as well. But as far as I know, one would only want to do that on a platform that doesn't support AIO. In either case, you chose one way or the other. But on this DB that I saw, both are set. So I am wondering which one will it use? I don't have enough permission on the system to truss the process or anything. So I wonder if anyone has seen it before and the implication of having both set.

Best regards

Richard Ji

On Wed, 8 Dec 2004 08:58:49 -0800, Jared Still <jkstill_at_gmail.com> wrote:
> I haven't worked on Solaris in awhile, so I don't n know
> if the following is true on your version of Solaris or not. I
> believe I last tested it on 2.6 or 2.7.
>
> Enabling disk_io_sync on Solaris does not not cause
> async IO on filesytems, only on raw disk.
>
> You may want to investigate.
>
> Jared
>
>
>
>
> On Mon, 6 Dec 2004 22:21:10 -0500, Richard Ji <richard.c.ji_at_gmail.com> 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.
> > --
> > http://www.freelists.org/webpage/oracle-l
> >
>
>
> --
> Jared Still
> Certifiable Oracle DBA and Part Time Perl Evangelist
>

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