Re: 9i's dynamic sga

In article <3D15BE67.1060506_at_europe.com>, sg says...
>
>does this apply to all platforms?
>

no, see
http://technet.oracle.com/docs/products/oracle9i/doc_library/901_doc/A90347-02/html/ch1_admi.htm#86752

for example where it discusses ISM vs DISM on solaris.

But -- bear in mind, that one a platform like windows where it must do this (in order to keep the memory space "flat" -- we cannot just realloc() the memory, it would move the entire SGA -- leaving a really big, huge hole in the processes already allocated memory), the OS will do the right thing. That is -- if we ask for 500m, but use only 200m -- the other 300m will be paged out, the OS won't reserve physical ram for us. If you never grow the SGA, that memory will never be paged in.

>cheers
>
>Howard J. Rogers wrote:
>
>> Yup.
>>
>> Set SGA_MAX_SIZE to X, and Oracle nabs the whole of X from the O/S, even if
>> then doesn't go on to allocate all of X to the various components of the
>> SGA. The 'show SGA' command then displays what has been reserved, not what
>> is actually in use (which is a shame, I think, but you leanr to live with
>> these things).
>>
>> It has to be this way (the reserving, not the displaying), because when you
>> dynamically increase the buffer cache or shared_pool, the granule
>> allocations have to be contiguous allocations of memory -contiguous, that
>> is, with what was already there.
>>
>> Regards
>> HJR
>>
>>
>> "sg" <s4v4g3_at_europe.com> wrote in message
>> news:3D14FFD2.2040303_at_europe.com...
>>
>>>Does anyone know if no matter how we set the shared pool and db cache
>>>Oracle's memory consumption at OS level will always equal to
>>>sga_max_size? I set a pretty low db cache and shared pool and a large
>>>sga_max_size and when I do show sga it actually syas that the
>>>sga_max_size sga is allocated. Does Oracle reserve sga_max_size memory
>>>at OS level since instance startup?
>>>
>>>
>>
>>
>

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