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Operating System - Tru64 Unix
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sem_mni - semaphore

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Respected Contributor

sem_mni - semaphore

I've searched the forum and can't find an answer.

The question is how can I determine what will be the impact of increasing the number of semaphores (sem_mni) on a Tru64 server ( V5.1 )?

I know the current sem_mni value is 32...we had just recently updated that from 16. The ongoing issue is that the Openview agent can't run because of a lack of semaphores.

I'm planning on doubling the number of semaphores to 64. But I don't have a sound reason for picking that number. So I have a secondary question....what's the best approach to determining a proper value for sem_mni?

The Devil is in the detail.
Rob Leadbeater
Honored Contributor

Re: sem_mni - semaphore

Hi Kevin,

I don't know what sort of value you should be picking, but a quick look at the man page for sys_attrs_ipc suggests that you might want to be looking at sem_msl as well as sem_mni.

Maximum number of System V semaphores that can be used by a single process at one time.

Default value: 25 (semaphores)
Minimum value: 0
Maximum value: INT_MAX

Hope this helps,


Vladimir Fabecic
Honored Contributor

Re: sem_mni - semaphore

What's the best approach to determining a proper value for sem_mni?
Read documentation of application you are going to run on that system, that is the best way.
So take a look at Openview client docs and set the parameters.
Do not worry, if you make the value bigger, nothing bad will happen.
In vino veritas, in VMS cluster
Ivan Ferreira
Honored Contributor

Re: sem_mni - semaphore

Increasing the number of semaphores won't harm, for example, in our database servers we have:

sem_mni = 1024

By oracle recomendation.
Por que hacerlo dificil si es posible hacerlo facil? - Why do it the hard way, when you can do it the easy way?
Respected Contributor

Re: sem_mni - semaphore

The Devil is in the detail.