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RE: Is nothing sacred? (Oracle vs The Experts)

From: Jesse, Rich <>
Date: Mon, 11 Nov 2002 12:43:35 -0800
Message-ID: <>

Actually, I did know about the BHR thing, primarily from this list, just as you did. It was the indexing one that cought me off-guard. I was just using the former as a reference.

Speaking of which, your Don Quixote reference is priceless! "Facts are the enemy of truth." :D

Rich Jesse                           System/Database Administrator              Quad/Tech International, Sussex, WI USA

> -----Original Message-----
> Sent: Monday, November 11, 2002 2:04 PM
> To: Multiple recipients of list ORACLE-L
> Subject: RE: Is nothing sacred? (Oracle vs The Experts)
> Rich - Actually, if you took an Oracle Performance Tuning
> class from Oracle
> Education right now, you would find the BHR mentioned little
> and Oracle
> waits emphasized a great deal. I took that class about a
> month ago and the
> instructor described how Cary had prevailed in convincing the
> people at
> Oracle that counted and the class materials were being
> rewritten for the
> next class after mine.
> Well, being a computer professional is a hard burden, what with the
> underlying assumption ever changing. Actually, given the extensive
> discussions we've had on this forum about BHR vs. waits, I'm
> surprised it
> caught you unawares. This was where I'd first heard about the
> new emphasis
> on waits. Of course, with waits becoming the conventional
> wisdom, Cary and
> others will have to find another windmill to tilt at. Cary -
> anything lined
> up?
> Dennis Williams
> DBA, 40%OCP
> Lifetouch, Inc.
> -----Original Message-----
> Sent: Monday, November 11, 2002 10:58 AM
> To: Multiple recipients of list ORACLE-L
> So, there I am, on (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

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Author: Jesse, Rich

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Received on Mon Nov 11 2002 - 14:43:35 CST

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