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Re: performance issues

From: Joel Garry <joel-garry_at_home.com>
Date: 6 Dec 2005 14:00:05 -0800
Message-ID: <1133906405.457063.112220@g43g2000cwa.googlegroups.com>


>I am not aware that recycle pool can help with DML. Could you please
>shed some light?

If you are doing mass updates of tables, they need to be read into the SGA. This interferes with the LRU algorithms for the OLTP tables, both in flushing them out prematurely and housekeeping. If you move tables and indices that are updated in mass quantities to the recycle pool, Oracle doesn't have to worry about keeping around buffers that are never touched or flushing out buffers that are touched repeatedly. Which means cutting down on I/O. See
http://download-west.oracle.com/docs/cd/B10501_01/server.920/a96533/memory.htm#33862 and Jonathan Lewis, among others (I don't know how out-of-date http://www.ixora.com.au/newsletter/2000_10.htm#cache is) have written details if you want to know what is really happening.

Now, if the tables being mass updated are the same ones being OLTP'd, you may have some design issues. I've heard tell of people running multiple instances on the same database so they can tune one for updates and one for reporting, but haven't tried such a thing myself.

How much physical memory are you actually using with 2.7G SGA and 100 users?

The big SGA is a lot less inefficient than in years past, see http://team.tusc.com/pls/inet/inet_Download_Info_pkg.Get_Info?in_item=nyoug2005-block_level_tuning.zip

jg

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Received on Tue Dec 06 2005 - 16:00:05 CST

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