RE: Problem with large SGA

I don't know that a large SGA in general will hurt performance but a large shared_pool in specific can cause problems.    

Jay Miller    

-----Original Message-----
From: zhu chao [mailto:zhuchao_at_gmail.com] Sent: Saturday, October 08, 2005 1:24 AM To: oracledba.williams_at_gmail.com
Cc: Thomas.Mercadante_at_labor.state.ny.us; daniel.hubler_at_aurora.org; oracle-l_at_freelists.org
Subject: Re: Problem with large SGA  

Large SGA does not hurt performance, for improvement, it depends on the active data set.

We have case increase sga size helps a lot, also cases double sga size does not help at all. With large SGA and large tablespace, begin backup is much longer than before. Even if you do a full checkpoint before you begin backup.  

On 10/8/05, Dennis Williams <oracledba.williams_at_gmail.com <mailto:oracledba.williams_at_gmail.com> > wrote:

Daniel,

> We recently increased the size of our SGA from 40gig to over 100gig by
> increasing our shared pool and block buffer cache.
> Everything has gone very well.

Have you had an opportunity to test your performance with large SGA? I've heard tales of people who have increased the SGA to the point that performance actually degrades. Like maybe buffer cache searches take a long time. Never had access to enough RAM to test this myself.

Recently this list had a thread discussing solid-state disk. It seems to me that you pretty much have that in this situation.

Dennis Williams

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Regards
Zhu Chao
www.cnoug.org  <http://www.cnoug.org> 




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