Re: What is the INSTANCES modifier of the PARALLEL clause?

From: Greg Rahn <>
Date: Mon, 31 Mar 2008 15:22:36 -0700
Message-ID: <>

I believe its deprecated. Used to be used with OPS (version 7 & 8) on IBM SP2.

If you want to "light it up" with PQ, just use "alter table parallel" which will set it to DEFAULT which is cpu_count * parallel_threads_per_cpu, which would default to 2 * # of CPUs. That is usually more than enough to saturate the IO channels.

On Mon, Mar 31, 2008 at 9:03 AM, Rich Jesse <> wrote:
> Hey all,
> I'm looking to implement parallelism for our largest tables in on
> AIX in order to more fully utilize our SAN. While continuing testing with
> various parameters, I've been seeing that there is an INSTANCES qualifier of
> the PARALLEL clause in the ALTER TABLE statement.
> >From experiment, it appears to affect whether or not parallelism is used for
> certain queries (I think there was just a thread here about that, but
> regarding the DEGREE qualifier). The kicker is that I can't find any
> documentation on INSTANCES.
> Docs on do not mention it in the 10.1, 10.2, or even the
> 11.1 version for the ALTER TABLE command, and a search for "parallel
> instances" is nearly futile with the number of unrelated hits on
> "instance[s]".
> Anyone have any pointers on this? Thanks!
> Rich


Greg Rahn
Received on Mon Mar 31 2008 - 17:22:36 CDT

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