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[Support #SQZ-815795]: Mcidas Shared Memory Requirements

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  • Subject: [Support #SQZ-815795]: Mcidas Shared Memory Requirements
  • Date: Mon, 18 Aug 2008 21:04:59 -0600
Hi Brendon,

re:
> I noticed in the Mcidas documentation requirements for shared memory
> size at
> http://www.unidata.ucar.edu/software/mcidas/current/users_guide/workstation.html
> as follows:
> 
> kernel.shmmax = 536870912
> kernel.shmall = 536870912

This is more of a guideline/recommendation than requiremet.

> I have CentOS 5.1 on my system, and the defaults in my sysctl.conf is
> the following:
> 
> # Controls the maximum shared segment size, in bytes
> kernel.shmmax = 4294967295
> 
> # Controls the maximum number of shared memory segments, in pages
> kernel.shmall = 268435456
> 
> The system itself has 16 GB of RAM, with another 2 GB of swap space.
> Just wondering if I should stick with the defaults already in my
> sysctl.conf,

Yes, I would stick with your defaults.  The comments about increasing shared
memory are aimed at Unix/Linux distributions that come configured out of
the box with very small amounts of shared memory.  Solaris is, perhaps,
the worst for this setup allocating only 1 MB or so by default.

> or if I can change it later after compiling & using Mcidas
> if I see problems.

You won't run into any problems.  Not having enough shared memory will cause
problems when the user tries to start a McIDAS session that needs more
shared memory than is available.  You will not run into this problem.

> Thanks,

No worries.

Cheers,

Tom
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Ticket Details
===================
Ticket ID: SQZ-815795
Department: Support McIDAS
Priority: Normal
Status: Closed