Re: BCHR Tuning

From: Robert Eskridge <bryny_at_dfweahs.net>
Date: Fri, 10 Jan 2003 08:14:30 -0800
Message-ID: <F001.0052C65E.20030110081430@fatcity.com>

Dan,

I apologize for not detecting the humor at first and giving a serious reply. Either I had some sort of weird window setting emphasizing the goofball portion of the message, or I need to tune my humor detector. (This is not a good sign on a Friday....)

-rje

F> Here's an excellent real life example of why BCHR is not a good tuning
F> metric and you should focus on reducing I/Os.
F> A simple fix for a query and here is the resulting email to the client, who
F> understands that BCHR is not good. A little techie humor...
 

F> I have good news and I have bad news.

F> The good news is that the elapsed query time and total I/Os for the latest F> iteration dropped significantly.

Old -->> 1:42 min 2,715,659 i/os (15,925 physical)

New -->> 22 seconds 3318 i/os (2861)

F> However, the bad news is that the Buffer Cache Hit Ratio dropped F> dramatically!

Old -->> 99.36%

New -->> 13.77%

F> So, I have undone all the changes I made and will begin looking at other F> methods to improve performance!

-rje

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Author: Robert Eskridge
  INET: bryny_at_dfweahs.net

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