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Subsequent starting and stopping dbsrv gives better performance

Posted on 2003-11-28
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Last Modified: 2012-08-13
I have a situation where some queries have a poor performance. (ASA6)
I discovered that if I start and stop the database 5 times, the performance is very good.
This trick does not work with two times, no, 5 times is needed to get the good performance.

How can this be explained?
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Question by:jvv
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DaniPro earned 250 total points
ID: 9848929
This is a strange situation, I'm suggesting you of verify the plan of your query when the database start for frist time and when the database start for tifth time.
After you can try to drop the database statistics [ DROP OPTIMIZER STATISTICS ].

Occasionally, the statistics may become inaccurate or relevant statistics may be unavailable. This condition is most likely to arise when few queries have been executed since a large amount of data was added, updated, or deleted.

In this situation, the best approach is to execute statements that allow Adaptive Server Anywhere to scan the new rows sequentially. The internal statistics are automatically updated as a side effect, allowing the optimizer to choose better plans for subsequent queries.

The DROP OPTIMIZER STATISTICS statement deletes all internal statistical data from the column statistics registry. This drastic step leaves the optimizer with no access to essential statistical information. Without these statistics, the optimizer may generate very inefficient data access plans, causing poor database performance.

This statement should be used only during problem determination or when reloading data into a database that differs substantially from the original data.


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