Re: how do I enable the Semphore - for oracle installation ?

From: Walter T Rejuney <BlueSax_at_Unforgetable.com>
Date: Wed, 18 Oct 2000 10:35:26 -0400
Message-ID: <39EDB52D.C2471C3@Unforgetable.com>

Dave A wrote:

> That's more or less my point. For The Oracle Instalation guide to require
> telling the OS to allow Oracle to use more memory than it has is bizarre.
> While I see no harm in allowing 80% of system memory to go to Oracle, I have
> no idea why anything more than the size of the sga would need to be set for
> this parameter.

Keep in mind that shmmax has no knowledge of Oracle. Any process that requests a shared memory segment can get this amount of memory. If the setting is too small then an error will be generated when shmget() is called. However, that is only an upwards limit, if the actual amount of memory is less than shmmax then it will still only get what it actually requests.

The reason that I set shmmax to 80% of physical is that because I don't don't like to size things so tightly that I don't have any room to make changes to the shared pool size without having to rebuild the Unix kernal if I should decide that I want to try a larger size.

On machines where shmmax is set to 80% of physical I have never seen any process run into an ENOMEM error unless some very funky things are going on with multiple processes trying to create shared memory segments. Received on Wed Oct 18 2000 - 09:35:26 CDT