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Message Posted: Thu, 07 Mar 2002 @ 23:04:27 GMT


     
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Subj:   Re: Users Having Spool Space Problems Under V2R4.1
 
From:   Warren Gilbert

We recently upgraded from a 4700 running V2R3.x to a 4855 running V2R4.1 and experienced a few similar problems.

Some of the problems were related to Small Table/Small Table/Large Table joins where the new system decide the best plan was to Product Join the 2 small tables causing either spool problems or extended execution times.

During the upgrade we had collected statistics on all the tables on the new system, so that was not the problem.

One of the tables involved was our own CALENDAR table which holds date information for about 9 years. We took a copy of the table and progressively added more years to it, collected statistics, re-ran Explain on the query until the Product Join disappeared when the copy table was 4 times its original size, and the query then ran OK. We then removed the additional years, but retained the statistics. Teradata thinks the table is 4 times its actual size. Only queries displaying this kind of problem were modified to use the copy table, everything else uses the original CALENDAR.

Also a handful of other queries which needed redesigning to avoid performance problems, one MLOAD which was updating 3 very wide tables which needed a re-write.

Probably a smoother upgrade than going from V2R2 to V2R3 on the 4700 system.

--
Warren GILBERT
Keighley, W Yorkshire, UK



     
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