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Re: RAC in NAS

From: Mark Brinsmead <>
Date: Fri, 28 Jul 2006 21:55:40 -0400
Message-ID: <>


   You are only *half* right, I fear.

   Actually, at least one of -- and perhaps both -- MetaLink and Werner describe more or less
the same caveat, that is: applications *other* than Oracle may be responsible for the non-zero
counts in slabinfo.

   But here's the half where you're wrong. (Or at least, not completely "right".) Those hypothetical
"other" applications can just as easily be resposibly for the *increases* in the slabinfo stats as
they are they would be for "non-zero" values. After all, those values had to increase from zero
*some* *time*, didn't they. ;-)

   Anyway, you are correct about this: I am still unaware of a simple way to prove *conclusively*
that a database is actually using Asynch I/O. But (on a good day) I now at least know how to
prove that it is *not*. (Or at least that *no* databases *are*. Sadly, multiple database on the
same host muddy the water even more.)

   If anybody out there can tell me of a simple (and reliable) test that *proves* a database is using
Asynch I/O, I'd like to hear about it...

   In the meantime, it has (happily) met my purposes to be able to prove the negative.

On 7/28/06, Nuno Souto <> wrote:
> Mark Brinsmead wrote,on my timestamp of 28/07/2006 1:39 PM:
> > (Almost) just for chuckles, I opened an SR with Oracle support, asking
> > questions like "how can
> > I test whether my DB is doing Asynch I/O on Linux?" and "knowing that
> > Asynch I/O is unsupported,
> > what are the risks of doing so anyway?". After almost two weeks, the
> > questions are unanswered,
> > even though I was able to answer them myself with less than an hour of
> > surfing Metalink and Google.
> yes, there is a note in metaclick explaining how to check.
> But it's not complete, neither is werner's site:
> you check for those counters in /proc/slabinfo being
> non-zero *AND* changing in value when you startup Oracle!
> There might be *other* software around already using aio
> and just having them as non-zero is not enough to say
> Oracle is using it.
> --
> Cheers
> Nuno Souto
> in (finally) sunny Sydney, Australia
> --

-- Mark Brinsmead
   Staff DBA,
   The Pythian Group

Received on Fri Jul 28 2006 - 20:55:40 CDT

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