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Message Posted: Wed, 06 Nov 2003 @ 00:08:25 GMT

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We had a query that ran out of memory for plastic steps after our upgrade. We traced it to the change in derived table handling between V2R4 (materialized as a table) and V2R5 (treated like a view substitution). The V2R5 solution allows the system to examine more of the query at one time, which may lead to better optimization, but you need more memory to do it that way.

The problem query had 1300+ lines containing many case statements doing code substitution, rather than using code table lookups. It also had a derived table containing a 16 table join with more case statements to supply the data. The user rewrote the SQL which solved the problem.

/dave hough

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