RE: Free memory

From: Bobak, Mark <>
Date: Fri, 19 Mar 2010 13:33:24 -0400
Message-ID: <>

Hi Joe,

That memory is reserved for Oracle's exclusive use. You can (should be able to) dynamically increase sga_target from its current setting to a max of sga_max_size, without a bounce.

But, as that memory is part of the shared memory segment that Oracle has allocated at instance startup, that's the only place the memory can be used.


From: [] On Behalf Of Joe Smith Sent: Friday, March 19, 2010 10:15 AM
Subject: Free memory

How does Oracle/SunSolaris handle the "Free SGA Memory available"?

My sga_target=384M


I use the ipcs -a command to see the size my of Shared Memory segment for the db:

SEGSZ=734011392 If I select from v$sgainfo:

Free SGA Memory Available 331350016

My question is:

My shared memory segment is 700M,
my sga_max_size is 700M,
my sga_target is 384M
my Free SGA is 316M

How does Oracle/Sun at the OS level handle that free memory in the shared memory segment? Is it reserved only for Oracle processes or can other users claim some of that memory if the system is under pressure? Does the OS "lock" or set aside that memory region and say "I know you are not using this now, but I am going to restrict access to it from other users and hold it for only you (i.e. Oracle processes ).


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-- Received on Fri Mar 19 2010 - 12:33:24 CDT

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