shmall on Linux recommendation

  • From: "Herring Dave - dherri" <Dave.Herring@xxxxxxxxxx>
  • To: "Oracle L" <oracle-l@xxxxxxxxxxxxx>
  • Date: Tue, 12 Jan 2010 09:54:27 -0600

Folks, I've inherited a 4-node RAC plus DG environment that has a rather 
curious shmall setting that I'd appreciate your thoughts on.  I've done my best 
to understand it's current setting but those that made the decision are no 
longer with the company and/or client.

The system is running on RHEL 4.  Like I said, it's a 4-node RAC, 64 
GB RAM, with the same for a physical standby.  Currently the SGA of each 
instance is 17 GB.

The install guide gives a minimum value of 2097152 (8 GB) while the current 
value is 25165824 (96 GB).  To me it seems just a wee bit aggressive to be 
setting the total shared memory to be RAM + swap!  MOS doc 301830.1 gives the 
recommendation of the SUM SGAs on the server, so in this case 4456448 (17 GB).

Sizing shmall to be the SUM of the SGAs on the server makes sense, but I'm 
curious if anyone has experience that suggests otherwise?  Also, can anyone 
think of a good reason to set shmall to RAM + swap (other than "'cuz it's 


Dave Herring  | DBA, Acxiom Database Services

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