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Message Posted: Sat, 24 Oct 2009 @ 18:45:59 GMT

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Hi,

"Performance TUNING" is same as "Query optimization".

"Dealing spool space errors": Spool Space Error is one of the issues that need "Query optimization/Tuning" to be done. Sometimes the queries may not spool out but might be taking longer than expected to complete OR some queries might be showing higher CPU Skew. In such scenarios too we need to Optimize/Tune the Queries.

For example, if there is a query that involves JOIN of two or more tables but the columns used in JOIN are NOT UPI/PI columns. If there are no STATS collected on such columns then the query may spool out OR it may take too much of time to complete. In such a scenario we should COLLECT STATS on such columns that are used in JOIN but are not part of UPI/PI of the tables.

In another example, we might be loading a table having SECONDARY INDEXES (SI) defined on it. This might make the query run slower. In such a case, we can drop the SI on the target table and then load the data in it. After loading the table, SI can again be created on the target table using CREATE INDEX statement.

Thanks

Lakhwant

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