Oracle-L: Changed execution plans..

From: Robert Freeman <robertgfreeman_at_yahoo.com>
Date: Sat, 18 Jan 2003 23:23:47 -0800
Message-ID: <F001.00533E9D.20030118232347@fatcity.com>

Hey Ya'all... (still got my southern roots even up here in Chicago!)

Anyone want to throw in some possible reasons why an execution plan might change for a given table query....This is on Oracle9iR2 on SUN. I've looked at the obvious causes:

Object has changed - Appears not to have changed.
Database parameters have changed - Appears that no parameters have changed.
Statistics (data volumes, distribution, cardinality, etc) have changed - Still looking into this, but the volumes have not changed dramatically even if they have changed.
Other physical database changes.

None of these seem to apply. I've got a database that a few weeks ago were doing indexed
lookups using a partitioned index on a partitioned table. Now, it seems that these queries
are doing full table scans on this partitioned table. I'm still gathering up the details for the items above (e.g how much have the objects changed) and I'll probably run a 10053 trace on one of the bad queries to see what the optimizer is doing on Monday, but I'd like to just poll for some additional ideas. I *AM* getting partition elimination (thank goodness) but I've got two FTS on one partition of this table that are just killing it. They want to quantify the reason why this access has changed so I'm trying to think of what kinds of stuff I can look at to try to do this.

I will add that this table was just rebuilt recently (through imp/exp)... can the change in row to block density make the difference.... hmmmm....

Any ideas??

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--

Author: Robert Freeman
INET: robertgfreeman_at_yahoo.com

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