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Operating System - Tru64 Unix
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Segmented Shared Memory Error

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Lou Carusone
Occasional Visitor

Segmented Shared Memory Error


I have a DS20E running Tru64 UNIX version 5.1A with patch kit 4 installed. We are also running Oracle 9.1i on this machine.

When I boot the machine I get the error "Segmented Shared Memory and Granularity hints are mutually excluseive turn off Granularity hints".

I have looked into the System Configuration Tuning Guide and found that for Granularity hints to be off the attribute gh_chunks must be zero. I checked the sysconfigtab file and also used sysconfig -q vm | grep gh and found that it is already a zero.

The machine seems to be working with no problems. Could someone tell me what might be causing this error.

Thanks in advance.
Hein van den Heuvel
Honored Contributor

Re: Segmented Shared Memory Error

With 5.1a the gh_chunks became obsolete in favor of rad_gh_regions[x].
Note: GH was always a stop-gap waiting for big-pages which are available with V5.1b.
Big-pages are pretty cool. Very flexible compared to GH. Rather efficient.
If you can get to V5.1b (PK2 or better) then please consider going there.

If you can't get to V5.1b, and you have a pretty intense oracle usage ( say more than 1GB SGAs and more than 30 concurrent sessions ) then IMHO you should consider going through the trouble of setting up GH (and thus clearing ssm_threshold and new_wire_method (vm).

I always check current settings with:

sysconfig -q vm | grep gh
sysconfig -q vm | grep big
sysconfig -q ipc | grep ssm

You'll need to grep sysconfigtab to learn about conflicting and thus ignored values.

Good luck,
Ralf Puchner
Honored Contributor

Re: Segmented Shared Memory Error

Please open a case at Oracle and check the recommended settings for the OS. There is a Oracle tuning guide and a list of necessary settings for each Tru64 version which will be offered by Oracle.

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