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Re: cost based optimization

From: <michael_bialik_at_my-deja.com>
Date: Mon, 30 Aug 1999 20:04:46 GMT
Message-ID: <7qeo4l$833$1@nnrp1.deja.com>


Hi.

 As far as I can remember - the default for EXPORT to  collect stats is ESTIMATE.
 I feel safer with COMPUTE.

 Michael.

In article <7qa5mg$4du$1_at_bgtnsc02.worldnet.att.net>,   "Jill" <jc_va_at_hotmail.com> wrote:
> I believe an import will populate the number of rows column in
DBA_TABLES by
> default, so unless you want histograms, I believe it's already
analyzed
> after an import.
>
> michael_bialik_at_my-deja.com wrote in message <7q9aqq$ko8
$1_at_nnrp1.deja.com>...
> >In article <37C7854E.BCD1E518_at_synergy-infotech.com>,
> > Anurag Minocha <anurag_at_synergy-infotech.com> wrote:
> >> Hi,
> >> I am a little confused about Cost Based Optimization.Please help me
> >out.
> >>
> >> 1.Does the cost based optimization work on those sql queries which
> >dont
> >> have hints specified in them.?
> >>
> >> 2. How frequently should the tables be analysed.
> >>
> >> Any help will be greatly appreciated.
> >>
> >> Thanks
> >> anurag
> >>
> >> also reply to
> >> anurag_at_synergy-infotech.com
> >>
> >>
> > Hi.
> >
> > 1. Yes. CBO works for queries accessing any of the
> > analyzed tables.
> > If you are making a join of n tables and only one of them
> > is analyzed - CBO assumes that all other tables have 0 rows
> > and usually uses FULL access for them.
> > 2. Analyze your table after EXP/IMP, initial load and any data load
> > that may affect data distribution.
> > Consider using "ESTIMATE STATISTICS" instead of "COMPUTE"
> > for large tables.
> >
> > Good luck. Michael.
> >
> >
> >Sent via Deja.com http://www.deja.com/
> >Share what you know. Learn what you don't.
>
>

Sent via Deja.com http://www.deja.com/
Share what you know. Learn what you don't. Received on Mon Aug 30 1999 - 15:04:46 CDT

Original text of this message

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