Re: HowTo find out used (useful) and unused (usesless) indexes?

From: Shakespeare <whatsin_at_xs4all.nl>
Date: Sat, 19 Apr 2008 11:37:36 +0200
Message-ID: <4809bd53$0$14352$e4fe514c@news.xs4all.nl>

"Malcolm Dew-Jones" <yf110_at_vtn1.victoria.tc.ca> schreef in bericht news:48091a22$1_at_news.victoria.tc.ca...
> joel garry (joel-garry_at_home.com) wrote:
> : On Apr 18, 2:29=A0am, Andreas Mosmann <mosm..._at_expires-30-04-2008.news-
> : group.org> wrote:
> : > Thank both of you,
> : >
> : > I will try it out.
> : > Is there also a way to determine what index is still needed/useful for
> a
> : > special query?
> : >
> : > Andreas Mosmann
> : >
> : > --
> : > wenn email, dann AndreasMosmann <bei> web <punkt> de
>
> : I do believe that is the downside of deleting indices based on usage.
> : It only shows what's been used during the observation. That implies a
> : bad assumption that the usage is completely stable. To me, this seems
> : worse than just dropping an index and seeing who screams, since when
> : there is a problem in the future, you have to go through an entire
> : performance tuning workup because the linkage to the act of dropping
> : the index is obscured. Maybe I'm missing the concept. What about an
> : index that would be used when you pass some tipping point or boundary
> : condition or upgrade or change a session parameter?
>
> You can disable an index. That way the definition exists but the index is
> never used or maintained (i.e. no overhead). If you decide it is needed
> you simply enable it.
>
> "when you pass some tipping point"
>
> If an index is enabled then presumably it will only be used when the CBO
> decides it is useful for a query.
>

But an index may become useful over time, true?

Shakespeare Received on Sat Apr 19 2008 - 04:37:36 CDT

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