RE: Questions about automatic memory allocations in 10g (r1 and r2)

From: Pete Sharman <peter.sharman_at_oracle.com>
Date: Fri, 21 Oct 2005 04:10:15 +1000
Message-ID: <20051021041015692.00000002116@psharman-au>

So all the DBA does now is manage memory? What a load of codswallop!

Well I could use other terminology but I might offend someone. :)

There's no way Oracle can use ALL of the physical memory for the SGA. IIRC, the default set up when you're using DBCA is 40% of the machine's memory. Actual details are in chapter 7 of the Performance Tuning Guide. Might be worthwhile starting there and coming back with questions if you still have them.

Pete

"Controlling developers is like herding cats." Kevin Loney, Oracle DBA Handbook

"Oh no, it's not. It's much harder than that!" Bruce Pihlamae, long-term Oracle DBA

From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Reidy, Ron Sent: Friday, 21 October 2005 2:15 AM
To: oracle-l_at_freelists.org
Subject: Questions about automatic memory allocations in 10g (r1 and r2)

Guys,
I was in a meeting yesterday with a vendor who told me (and my manager) their product running on 10gr1 does not need any DBA intervention when used because they are using automatic memory management and they use "all of physical memory . for the SGA". Now, this person is no Oracle DBA/expert/guru. He has attended a class like "New features in 10g" or something like that. When I questioned this "use all of physical memory" strategy and how that might affect PGA usage, he was stumped. Well, this meeting got me to thinking about if this really works or not, so I went and read up on this new feature on http://tahiti.oracle.com. My concerns about this center around questions like:

1.  Does this really work? 
2.  How often is the memory usage looked at and adjusted? 
3.  When an adjustment (shrink) occurs in the shared_pool, are the cached SQL invalidated? 
4.  When the buffer_cache shrinks, are the buffers marked as dirty?

Does anyone know about these issues? Can you point me to somewhere where I might get answers to these questions or set up my own test case to show how this "feature" might work? Thanks for any time and effort put into this.

Ron Reidy
Lead DBA
Array BioPharma, Inc.

--
http://www.freelists.org/webpage/oracle-l

Received on Thu Oct 20 2005 - 13:13:02 CDT