Re: Oracle 7's cost based optimizer

In a previous article, dirkt_at_srs.gov ("R. Dirk Tolson") says:

>This is probably a FAQ but since there isn't one:
>
>This is the first week that we have had Oracle 7 running in production here and
>it has been quite a week. We have seen forms and reports that, though not
>'snappy' in the first place, have taken quite a hit in performance. System
>tuning was immediately begun and addressed some of it. Yesterday one of our
>DBAs tracked down another who had made the same transistion and taken the same
>performance hit. They tracked it down to the cost-based optimizer. Last night
>it was turned off here and we are awaiting results.
>
>In the mean time what experiences have others had with Oracle 7 and the new
>optimizer? What steps have you taken to optimize performance? Are there other
>gotcha's out there?
>
>TIA
>
>// dirk tolson
>// dirkt_at_srs.gov
>
>
>
>

One thing that might help is to ANALYZE the tables. You can do them all at once, look it up in the manuals. Basically, the cost-based optimizer does not work efficiently if the ANALYZE command has not been run because it is guessing at the statistics for your tables. With accurate statistics, it works much better.

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Diana Tracy, System Designer		-- Excitement, Adventure
bs794_at_cleveland.Freenet.Edu		-- and Really Wild Things