From: Jerry Gitomer <jgitomer@p3.net>
Subject: Re: Extents: Less or More?
Date: 1998/02/02
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Hi Phil,

I had the misfortune to get nailed by an excessive number of extents
problem in a purchased application.  The application was written in
a manner that caused a few of the columns in the row to be entered
initially and then added additional columns at separate times over
the course of the day.  By the end of the day the main table had
grown from one extent to seventeen :-(  

The clerks who were doing the data entry complained that the time
to enter the data for one event went from under ten seconds in the
morning to several minutes by late afternoon of the next day.  I 
wasn't able to go into the application and make any changes and the
vendor was clueless as to both the cause and how to cure it.  (It 
seems as though they hired a self-proclaimed Oracle whiz to do their
data base -- and he wasn't)  All I could do was a daily export and
import in order to reduce the number of extents.  It worked well
enough to keep the time required to enter data for an event stayed
under one minute.

Regards

Jerry



Phil Herring wrote:
> 
> In article <34d4ded2.0@news1.ibm.net> Brian S. Hummer, hummerb@usa.net writes:
> >[...] But recently, while taking the DBA course at
> >an Oracle Education center, I was lead to believe that the number of extents
> >for an object doesn't really matter.
> 
> That's about right, assuming that you're talking about all the extents being
> located on one disk (which is not always a valid assumption). There may be
> a small effect either way, depending on the application, but I don't see
> how it could be a significant consideration in the majority of cases.
> 
> For the record - I *never* compress extents. I've never seen it have any
> positive benefits, and I have seen it create problems, so my own philosophy
> is to leave them alone. The only qualification to that is when tables get
> too close to MAXEXTENTS, but when that happens, I usually rebuild the table
> with multiple extents and a larger INITIAL and NEXT, rather than forcing
> the table into one large extent.
> 
> ---------------------------------------------------------------------------
> Copyright 1998 Phil Herring. This article may not be reproduced for profit.
> ---------------------------------------------------------------------------