RE: Solaris 10 shmmax

  • From: "Bobak, Mark" <Mark.Bobak@xxxxxxxxxxxxxxx>
  • To: <Amir.Hameed@xxxxxxxxx>, "Kevin Closson" <kevinc@xxxxxxxxxxxxx>, <ax.mount@xxxxxxxxx>, <oracle-l@xxxxxxxxxxxxx>
  • Date: Mon, 26 Mar 2007 14:37:03 -0400

Yeah, I'm familiar w/ Bob's paper.  Bob actually got it wrong, as you
can see if you follow the link to Steve Adams' site that you provided,
and actually read what's written there......

Mark J. Bobak 
Senior Oracle Architect 

"There are 10 types of people in the world:  Those who understand
binary, and those who don't." 



From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Hameed, Amir
Sent: Monday, March 26, 2007 1:31 PM
To: Kevin Closson; ax.mount@xxxxxxxxx; oracle-l@xxxxxxxxxxxxx
Subject: RE: Solaris 10 shmmax

U are probably right Kevin that this feature should not be disabled
unless there is an absolute reason not to use it. There was a paper
written by Bob Sneed a while ago where he had stated that multiple
shared memory segments can impact performance. Steve Adams has also
quoted him on his site:
Bob's white paper:
This may not be an issue anymore.


        From: Kevin Closson [mailto:kevinc@xxxxxxxxxxxxx] 
        Sent: Monday, March 26, 2007 1:22 PM
        To: Hameed, Amir; kevinc@xxxxxxxxxxxxx; ax.mount@xxxxxxxxx;
        Subject: RE: Solaris 10 shmmax


        I would also like to understand this a little better. One of my
friends is running on Solaris9 and Sun 6900. His shmmax is set
to 20G and has 64GB RAM on the server and this is the only instance
running on that box. He is seeing multiple shared memory segments on the
server. Oracle told him to disable _enable_NUMA_optimization parameter
which is enabled by default.


        ...why? Why turn off the ability for Oracle to exploit the
hardware acrchitecture? Is the output of ipcs so disturbing due to
multiple segements?  That just sounds like concern over nothing.


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