Marlene and I did "exploding the myths" a while back and Jeremiah
Wilton did a myths presentation at OOW last year as well.
Rachel
- Jeffery Stevenson <dba_at_darkora.net> wrote:
> Well, besides the paper you found, Jonathan Lewis has a myths section
> with
> his site:
> http://www.jlcomp.demon.co.uk/myths.html
>
> Gaja also has a good "myths" article:
> http://www.quest-pipelines.com/newsletter-v3/0302_F.htm
>
> Rachel, weren't you doing a presentation on Oracle myths (or did you
> just
> put that in DBA 101)?
>
> Jeffery Stevenson
> Chief Databeast Slayer
> Medical Present Value, Inc.
> Austin, TX
>
> ----- Original Message -----
> To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com>
> Sent: Monday, November 11, 2002 10:58 AM
>
>
> > So, there I am, on 8.1.7.2 (and .4) on HP/UX 11.0, with a process
> that
> runs
> > 20 minutes out of every hour of the day (despite my protests to
> it's
> > design). After it starts having problems (go figure), it becomes a
> priority
> > to speed it up.
> >
> > Thanks to a 10046 trace, we see that the query taking the most
> elapsed
> time
> > does FTSs on each of two very small tables (1 block and 4 blocks --
> 8K
> > blocksize). These tables are not indexed, as per the official
> Oracle
> > recommendation. After reading the excellent Hotsos paper "When to
> index a
> > table" (THANKS, CARY!), I added an index to reduce elapsed time on
> this
> > query by 50% (150 to 75 seconds in test), proving to me that the
> paper is
> > valid. And I've only read to page four!
> >
> > OK, first I'm taught by Oracle to look at Buffer Cache Hit Ratios
> as a
> > measure of performance, then told (and thoroughly convinced) by
> experts
> that
> > this is bunk. Now, I found out that the 15% (or 10% or whatever,
> depending
> > on version) ratio of rows returned to total rows in determining
> when to
> use
> > an index in a query is garbage.
> >
> > 1) Why is this?
> >
> > 2) What other pearls of performance wisdom from Oracle Corp should
> I
> > completely disregard as false?
> >
> > I know there's an Oracle Fallacy website somewhere...
> >
> > It just looks bad on me, our department, and Oracle when, once
> again,
> > something I've been preaching to our developers as gospel turns out
> to be
> > completely false.
> >
> > Maybe I'm grumpy because it's snowing on my leaves right now...
> <sigh>
> >
> >
> > Rich
> >
> >
> > Rich Jesse System/Database Administrator
> > Rich.Jesse_at_qtiworld.com Quad/Tech International,
> Sussex, WI
> USA
> >
> > Disclaimer: I only said the Packers would be 12-4 this year -- I
> never
> said
> > that they couldn't do better! WOO-HOO! :)
> > --
> > Please see the official ORACLE-L FAQ: http://www.orafaq.com
> > --
> > Author: Jesse, Rich
> > INET: Rich.Jesse_at_qtiworld.com
> >
> > Fat City Network Services -- 858-538-5051 http://www.fatcity.com
> > San Diego, California -- Mailing list and web hosting
> services
> >
> ---------------------------------------------------------------------
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> >
> >
>
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.com
> --
> Author: Jeffery Stevenson
> INET: dba_at_darkora.net
>
> Fat City Network Services -- 858-538-5051 http://www.fatcity.com
> San Diego, California -- Mailing list and web hosting services
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Do you Yahoo!?
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--
Please see the official ORACLE-L FAQ: http://www.orafaq.com
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Author: Rachel Carmichael
INET: wisernet100_at_yahoo.com
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Received on Mon Nov 11 2002 - 12:44:13 CST
