Re: Cost Based Optimizier

From: Doris Jetz <djetz_at_spots.ab.ca>
Date: 1996/07/31
Message-ID: <4to28f$p0g_at_nr1.vancouver.istar.net>#1/1


I mentioned somewhere else in this newsgroup a while ago and I think it might be useful here.

When analyzing tables, don't use estimate, use compute on all tables any time you analyze for statistics. This is coming from a local (here in Calgary) oracle technical expert. He said that the estimates aren't accurate enough at this point and may result in really crappy execution paths.

Hope this helps.

Doris Jetz

richu_at_msn.com (Richard Hu) wrote:

> We have a 7.1.3.2.1 production system and have just ANALYZED all the
> tables and indexes.
> Since we have done this we are suffering with response times from queries
> that join two and more tables.
> When EXPAINed/TKPROFed we have discovered that some selects are
> performing full tables scans.
> It appears that the execution plans worked out by the optimizer are not
> the best.
> (I have checked that all the tables and indexes are analyzed -
> the statistics were ESTIMATEd on all but one table which was be
> COMPUTEd.)
>

Oracle DBA/Developer
NGX Canada Inc.
Calgary, AB Received on Wed Jul 31 1996 - 00:00:00 CEST

Original text of this message