Re: Memory limitations in Oracle?

On Tue, 27 Mar 2001 20:14:54 +0200, in comp.databases.oracle.server you wrote:

I have read the docs. My question is generic in nature. Not specific to any particular platform. Just curiosity.

1. Is SGA sizing a exact science or more of an art? Start off with 1/3 of RAM, monitor the hit ratio, increase, and repeat? Or is there a more methodical approach?
2. What is the rationale behind the "1/3 of RAM" rule of thumb?
3. You say "Oracle will not use 200GB". Is this a documented limitation in Oracle? I realize that throwing memory at the problem wont remedy poor application design. Again, my questions are just out of curiosity than anything else.
4. How much memory do the shadow/background processes need? Again, is there a methodical approach to determine this?

Thanks

>> Understood. What I meant was that assuming the OS supports it, is
>> there any *Oracle* limitation on using any amount of memory? f.i., if
>> the machine has a 200GB RAM, can Oracle use it all?
>>
>> >Oracle will refuse to start unless it can allocate all memory without
>> >paging to disk. However, allocating all your RAM to Oracle's SGA is
>> >probably an unwise decision, what are the Oracle shadow processes going
>> >to use, let alone any other process you might want to run?
>>
>> Hm. How do you size the memory used by the shadow processes?
>>
>> In general, how is the SGA sized? Bumping it up upon discovering a
>> poor hit ratio is a reactive approach. What is the best-practice
>> approach for up-front design? Rules of thumb?
>>
>> Thanks...
>>
>
>If you would only first read the documentation from Oracle pertinent to your
>platform (which you of course don't mention), they you would know most of
>the answers.
>BTW rule of thumb is not to use more than 1/3 of physical RAM and I am sure
>Oracle won't use 200G.
>Also those monstrous amounts of RAM won't remedy bad application design.
Received on Tue Mar 27 2001 - 15:19:48 CST