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Any known issues to be careful about when gathering statistics for the optimizer to use ?
One thing I came across it not to generate stats for SYS. That's fine! When doing this for end users, any pitfalls to be careful about ? Can we rollback if application users face problems owing to this ?
Thanks.
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You can not rollback but you can delete the statistics.
Sanjay
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After using delete stats. . .
Analyze < name> delete statistics;
I will be in square one and appln. users will will be accessing their objects as if no stats. had been generated ?
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You CAN rollback the statistics if gathering new stats makes your performance worse (it can!). But first you have to save them. Refer to the DBMS_STATS package about how to save statistics to a table so that you can reapply them if you need. In short order you want to
1. Save stats to a stats table
2. Delete stats (to clear out the histogram buckets)
3. Analyze new stats.
4. Do a sanity check to make sure you haven't made performance worse.
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