Re: oracle 10g and db_keep_cache_size obsolete ?
Date: Wed, 29 Jul 2009 14:02:03 -0500
I agree with Mark. The keep pool when properly managed to help performance, as can the recycle pool. However since usage can change over time, the dba also needs to monitor the usage of the keep and recycle pools to make sure that the objects in each are appropriate.
On Wed, Jul 29, 2009 at 12:34 PM, Bobak, Mark <Mark.Bobak_at_proquest.com>wrote:
> I agree with Ric. I have used both keep and recycle to good effect, and
> still do, on 10g, by staying away from auto memory management.
> My philosophy is to try to fill KEEP up to the brim, mostly with heavily
> used small indexes, but very not to over-allocate it too much, while
> assigning the really huge objects with lots of small randomized reads to
> RECYCLE. The idea being that for the small indexes, you want them cached
> all the time, if not the entire index, then at least the root and first
> level branch blocks. In the case of the giant, way-too-big-to-cache
> segments, heap 'em in RECYCLE, and at least you limit the damage to those
> objects themselves, which would otherwise totally thrash the default cache.
> Having never used it, I'm no expert on automatic memory management (call me
> a typical DBA w/ control freak tendencies, I don't want Oracle deciding to
> move stuff around on me!), but I think a good DBA, with a solid
> understanding of the application, can use KEEP and RECYCLE and beat the
> performance of Oracle's automated memory management algorithms. The DBA
> simply has more information about the application and how it works, and
> expected usage patterns of various segments.
> -----Original Message-----
> From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org]
> On Behalf Of Ric Van Dyke
> Sent: Wednesday, July 29, 2009 1:10 PM
> To: Jon.Crisler_at_usi.com; ORACLE-L
> Subject: RE: oracle 10g and db_keep_cache_size obsolete ?
> * Would you consider db_keep_cache_size old-school and unneeded for 10g
> if your doing auto memory management? *
> Yes, however to say its obsolete is likely a stretch. The most common
> problem I run into is folks really don't understand what is going on in
> the KEEP pool. They load it up thinking that it will all "magically"
> stay in cache. Putting too much in there (as it sounds like you have run
> across) will make it act like the default pool, and likely worse since
> as I recall there are fewer latches allocated to the KEEP pool. Used
> very specifically it can be of some benefit. Same for the RECYCLE pool
> as well.
> Ric Van Dyke
> Hotsos Enterprises, Ltd.
> -----Original Message-----
> From: oracle-l-bounce_at_freelists.org
> [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Crisler, Jon
> Sent: Wednesday, July 29, 2009 12:55 PM
> To: ORACLE-L
> Subject: oracle 10g and db_keep_cache_size obsolete ?
> Looking for opinions- would you consider db_keep_cache_size old-school
> and unneeded for 10g if your doing auto memory management ? We rarely
> do this but ran across an app that has a lot of tables set to use the
> KEEP pool, and I am having a difficult time finding enough memory to
> satisfy the keep tables and a reasonable db_cache as well. My feeling
> is to just get rid of it since I wind up starving the rest of the
> database for tables with a DEFAULT pool.
-- Andrew W. Kerber 'If at first you dont succeed, dont take up skydiving.' -- http://www.freelists.org/webpage/oracle-lReceived on Wed Jul 29 2009 - 14:02:03 CDT