Re: shmmax sizing recommendations

From: Greg Rahn <>
Date: Wed, 18 Nov 2009 07:37:09 -0800
Message-ID: <>

On Wed, Nov 18, 2009 at 6:56 AM, Don Seiler <> wrote:
> I'm wondering what the masters out in the field think.  Would you
> advise setting SHMMAX to fit the largest SGA?  Is there any known
> performance hit by having more, smaller segments for an instance
> rather than 1 large one?

In the past I have set SHMMAX to either 1) the physical ram or 2) theoretical limit. Since this is simply an upper limit, it really has no performance "hit" for setting it too high.

There is some overhead in having multiple shared memory segments vs. a single one (for any given instance) but I dont have any numbers in my pocket to qualify that.

Greg Rahn
Received on Wed Nov 18 2009 - 09:37:09 CST

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