| Abt optimizer [message #20499] |
Thu, 30 May 2002 02:38  |
shyampaliyath
Messages: 22
Registered: May 2002
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Junior Member |
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hai,
is it good practise to use optimizer? becoz i don't find many of them using that.
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| Re: Abt optimizer [message #20510 is a reply to message #20499] |
Thu, 30 May 2002 11:59  |
andrew again
Messages: 2577
Registered: March 2000
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Senior Member |
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Yes, it is good to use the cost based optimizer. The rule based oprimizer is less accurate generally. To use the cost based optimizer you need to keep your table stats relatively fresh (analyze tables after big changes in the data quantities or distribution).
There are several different levels of analyzing tables.
-- for table and indexes
analyze table tt estimate statistics
-- for table only
analyze table tt estimate statistics for table
-- for indexes only
analyze table tt estimate statistics for all indexes
-- for index histograms
analyze table tt compute statistics for all indexed columns
-- everything
analyze table tt compute statistics for table for all indexes for all indexed columns
etc...
DBMS_STATS package is similar to the analyze command (and newer)
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