Re: Questions on ORACLE SGA size

Chang <changj_at_shell.ca> writes:

>Does anyone out there have answers to the following questions on SGA?
> 1. the theoretical maximum Oracle SGA size, assuming
> physical hardware memory is not a constraint
> 2. the practical limit, and the technical,operational and
> the performance implications of a huge SGA
> 3. what is the largest known SGA in operation?
 

>Thanks very much,
>Ji-Wui Chang
>_at_changj.shell.ca

Be very careful cranking up your SGA. I have never experienced a problem with large SGA values, depending upon the amount of memory is available on the system. I usually jack up SGA until I am getting about 90% cache hit ratios. SGA shares memory with the OS; when I was a DBA newbie, I decided to make SGA nearly equal to the machine RAM, the system stopped cold. Later, I realized there was not enough memory for the OS to allocate to semaphores and background processes. The largest SGA I have every used was 170MG on a 200MG RAM Novell server. There were major problems, because V7 and Novell tend to fragment memory when it gets >100.

Dagmar Anne Bogan

Kopania & Komorovsky          Specializing in Data Architecture
Richardson, TX  75081         and Performance Engineering

dagmara_at_delphi.com Received on Thu Jul 27 1995 - 00:00:00 CEST