Re: Oracle SGA size on i386 platforms

"Tim X" <timx_at_spamto.devnul.com> wrote in message news:877jjcy71k.fsf_at_tiger.rapttech.com.au...
> "Dave" <x_at_x.com> writes:
>
>> "Tim X" <timx_at_spamto.devnul.com> wrote in message
>> news:87ekdmxl4m.fsf_at_tiger.rapttech.com.au...
>>>
>>> Hi All,
>>>
>>> Just wondering if I can get some clarification on SGA size limits in
>>> Oracle 9i running on i386 based platforms (Windows and Linux). I've
>>> been told there is a 2Gb limit on both these platforms - though there
>>> does seem to be some workarounds under windows which will allow you to
>>> get to 3Gb.
>>>
>> there is a 1.75 gb limit on 32bit systems, without some fancy relinking
>> on
>> linux or playing with windows
>>
>> no gotchas (hate that term) on windows, if you understand windows - will
>> work well for you.
>>
>> Why do you think you need a bigger than 4gb SGA?
>
> Thanks. its not certain we need a larger than 4Gb SGA. We are
> currently running a 4Gb SGA - originally we started with just 2Gb, but
> this has slowly been increased as we tuned the config. On the current
> platform, we cannot go above 4Gb because we are still running an 8i
> database on this system and to go above 4Gb, there are some OS config
> changes required that then prevent 8i from being able to run at
> all. However, our senior DBA would like to have the flexibility of
> being able to go higher - especially as there is some functionality in
> the app we have not yet enabled because we don't feel we currently
> have the processing power to support it.
>
> Probably our biggest concern is that if we move to a 32bit platform,
> will we be able to get acceptable performance. The application we are
> running is not supported for Oracle RAC, so we cannot cluster the
> system (though they are promising both a RAC and AMD64 bit supported
> release by the 3rd quarter of 2006). However, we cannot wait until
> then as our current performance is unacceptable and having an adverse
> impact on the business.
>
> We are currently running the application on an Alpha ES40. The server
> also has a number of other Oracle based apps, though they are quite
> low demand ones. The ES40 has 4 733Ghtz CPUs and 30Gb of memory. Our
> average load has gone from 5 prior to this new application to an
> average of around 50 with extended peaks of 70 to 80. Performance is
> unacceptable. Our analysis indicates the primary bottleneck is CPU
> based, not memory or disk i/o. With a 4Gb SGA we are getting
> excellent cache hit ratios and minimal disk i/o. The application also
> uses 9iASr2, but our analysis indicates this only has a negligable
> impact on the system.
>
> Our plan is to move the DBMS onto either a windows or linux
> platform. The vendor does not support Linux at this time, but they do
> support windows. We would like to go to 64bit Linux running on a 4-way
> opteron, but if we want to stick with a supported platform, it has to
> be 32 bit windows and we are concerned about the impact of an SGA
> which will be less than half our current config.
>
> Tim
>

What do you mean "the vendor does not support Linux at this time" ? How about changing vendor ? You should choose your platform based on your current needs, not the other way around. Btw Windows Server 2003 also exists in a 64-bit version.

Matthias Received on Sat Apr 09 2005 - 12:35:30 CDT