shm_max > Physical Memory?

From: Skulley, William <William.Skulley_at_rfets.gov>
Date: Fri, 07 Sep 2001 15:02:02 -0600

UNIX 4.0D, Alpha 4100

My Oracle DBAs are asking to increase the value of shm_max to a value
greater than the physical memory in three of our systems (in one case,
greater than physical and swap combined). This seems obviously unwise to
me, but I am unable to find information in sys_attrs_ipc and the System
Performance and Tuning book that states clearly this is a Bad/Useless Thing.
Does a System V Shared Memory Region get allocated/reserved in its entiretly
when asked for, or is that value a maximum to which it can be allocated as
needed? The systems are dedicated Oracle database servers. Is this
something I should attempt to prevent?

Thanks
Bill Skulley
Received on Fri Sep 07 2001 - 21:03:06 NZST

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