Re: consistency in cost?

From: Rachel Carmichael <carmichr_at_hotmail.com>
Date: Wed, 09 May 2001 16:18:00 -0700
Message-ID: <F001.002FE9C8.20010509161529@fatcity.com>

woo hoo! Bambi's back and we've got her! :)

welcome home, you've been missed

>From: "Bambi Bellows" <ultrageek_at_techie.com>
>Reply-To: ORACLE-L_at_fatcity.com
>To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
>Subject: Re: consistency in cost?
>Date: Wed, 09 May 2001 14:31:01 -0800
>
>Tim --
>
>Oh, sure, bring LOGIC into it. Truth of the matter is that Oracle is
>trying to phase out the last vestiges of v5, and that's never EVER going to
>happen. Logic be dammed! Mwahahahaha!
>
>Bambi.
>
>------Original Message-----
>Date: Wed, 09 May 2001 05:01:06 -0800
>To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
>
>
> > Interesting...CHOOSE means Oracle will decide whether to use RULE or
>COST. But a CHOOSE hint will force use of COST. Kind of diminishes the
>meaning of CHOOSE, doesn't it? Seems like a pointless hint...
> >
> > >>> rabbit_at_emirates.net.ae 05/08/01 11:45PM >>>
> > If the system is Rule based and you code Hints, the CBO will be
> > automatically invoked
> > Sam
> >
> >
> > ----- Original Message -----
> > To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com>
> > Sent: Tuesday, May 08, 2001 10:12 PM
> >
> >
> > > Forgive my ignorance but I thought hints were only for cost based
> > optimizer.
> > >
> > >
> > > Have you checked in case anybody has changed any parameters while the
> > system
> > > is running as I know that changing the hash_area_size can change the
> > > execution plan?. Are you using parallelism as if a table had to be
> > > recreated for any reason and its degree changed it might do a FTS?
> > >
> > > Cheers
> > >
> > > Iain Nicoll
> > >
> > >
> > > -----Original Message-----
> > > Sent: 08 May 2001 17:31
> > > To: Multiple recipients of list ORACLE-L
> > >
> > >
> > > Jared,
> > > The only difference is about a weeks worth of extra data. Well, the
> > hardware
> > > is also different (Ultra450 vs. Ultra 5000. Also 1 vs 4 CPU). But
> > > regardless, shouldn't init.ora optimizer_mode=choose be identical to
> > > optimizer_mode=rule with hint=choose? If I have the time, I'll try to
>set
> > up
> > > a couple of systems and examine by moving stats and taking some 10053
> > dumps.
> > > (one of the ones giving me a problem is in production so I have
>limited
> > play
> > > time there).
> > >
> > > Henry
> > >
> > > -----Original Message-----
> > > Sent: Tuesday, May 08, 2001 12:56 AM
> > > To: ORACLE-L_at_fatcity.com; Henry Poras
> > >
> > >
> > >
> > > Henry,
> > >
> > > You say 'nearly identical'.
> > >
> > > What are the differences?
> > >
> > > Are the 2 databases on the same platform?
> > >
> > > If not, what are the differences, hardware and OS?
> > >
> > > Jared
> > >
> > >
> > > On Monday 07 May 2001 21:55, Henry Poras wrote:
> > > > I am working with an 8.1.6 database on Solaris 2.6 and I am
>wondering if
> > > > there is any consistency in the optimizer. We have two nearly
>identical
> > > > databases (one a clone from two weeks ago). A five table join has
>nearly
> > > > the identical execution plan on the two databases. The difference is
>in
> > > the
> > > > access method of the fourth table in the join; in one case it is
> > accessed
> > > > by a FTS and in the other, by Index. This difference has a large
>effect
> > on
> > > > performance. Statistics are nearly identical for this table in both
> > > > databases (I looked at dba_tables, dba_indexes, dba_col_tables).
>Also,
> > the
> > > > init.ora is the same. When I changed the optimizer_mode to rule and
> > added
> > > a
> > > > 'choose' hint to the query, the execution plan was different again.
>I
> > will
> > > > look into this a bit further and post my results. Just wondering
>about
> > > > other's experiences. Thanks.
> > > >
> > > > Henry
> > > --
> > > Please see the official ORACLE-L FAQ: <A HREF="http://www.orafaq.com"
>TARGET="_new">http://www.orafaq.com</A>
> > > --
> > > Author: Henry Poras
> > > INET: Henry.Poras_at_ctp.com
> > >
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> > > Author: Nicoll, Iain (Calanais)
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> > Author: Sam Roberts
> > INET: rabbit_at_emirates.net.ae
> >
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> > Author: Tim Sawmiller
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> >
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>
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>Please see the official ORACLE-L FAQ: http://www.orafaq.com
>--
>Author: Bambi Bellows
> INET: ultrageek_at_techie.com
>
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-- 
Author: Rachel Carmichael
  INET: carmichr_at_hotmail.com

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Received on Wed May 09 2001 - 18:18:00 CDT