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Message Posted: Tue, 13 Jun 2000 @ 18:28:18 GMT

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Subj:   Re: Hot Amp
From:   Eric J. Kohut


Hot amps are usually produced when data is redistributed to another amp in preparation for the next join step.

In order to know for sure, I would need the following.

Show table for all tables in query
Statistics for all tables in query
Help index for all tables in query

In most cases, what happens is that you have a large table being joined to a medium or small table and the optimizer chooses to redistribute the large table for one of several reason. The easiest to fix is to make sure you have collected statistics on all columns especially the Primary Index of small and smaller-medium size tables. You should also collect statistics for at least the Primary index of all medium sized tables.

When you say you can't change anything. Does this include the Primary index. Often you don't need to have a UPI, and having a NUPI can help improve performance substantially, but this will be dependent upon you queries.

Also, you can check with your local Customer Service support person and see if the Hash Join feature has been turned on. This approach can often help with these types of problems.

Finally, You'll still want to exclude the null since they will never join anyway. Then you can at least tune for the remaining data problem.



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