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Is nothing sacred? (Oracle vs The Experts)

From: Jesse, Rich <>
Date: Mon, 11 Nov 2002 08:58:28 -0800
Message-ID: <>

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 Jesse                           System/Database Administrator              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! :)

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Author: Jesse, Rich

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