RE: Very Strange Query Access Plan

Can you provide us with a (couple of) example(s) of these queries?

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Van: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org]Namens Mercadante, Thomas F (LABOR) Verzonden: dinsdag 2 oktober 2007 17:12
Aan: oracle-l_at_freelists.org
Onderwerp: Very Strange Query Access Plan

All,  

Running on 9.2.0.7 on Aix.  

I have a database table with 18 million rows in it. There is an SSN column in the table. Only 625,000 rows have an SSN populated. I also have an index on this column. Statistics on both the table and index are gathered nightly (using dbms_stats with the estimated and default sample options).  

Yesterday, queries against this table used the index. Today, they do not. There was no large data load overnight. We add about 10,000 records per day. This behavior has happened before where the index gets ignored for a day and then used the next day.

I really need to use an index here. Queries via ssn are executed all day long and take 10 minutes to complete. CPU is pegged at 99%.

What am I missing? Maybe histograms? Haven't used them before, so any suggestions would be helpful.

Thanks

Tom

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http://www.freelists.org/webpage/oracle-l Received on Tue Oct 02 2007 - 12:58:40 CDT