RE: Query tuning exercise: what to look for in a 10053 trace

You may be able to figure it out with a 10046 trace and a simple explain plan on the statement, then compare the estimated cardinalities to the actual number of rows returned from each step and most likely there will be a significant difference between the estimate and the actual in at least one place and that will usually point you in the right direction. From there you have to figure out why the estimate is off - probably due to skewed data - then see if histograms will help, or if you have to hint the SQL or use stored outlines (or SQL profiles in 10g). I don't have much experience with the 10053 trace either so can't really help you on that one. Wolfgang Breitling has a good white paper on it that you might find useful in case you haven't already read that - should be able to find it on google.  

Regards,
Brandon  

From: Schultz, Charles
Sent: Tuesday, July 25, 2006 12:39 PM

I have a query that is going bad when new stats are gathered on the underlying tables. I checked the stats, and they seem accurate.

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