Re: HowTo find out used (useful) and unused (usesless) indexes?
Date: 18 Apr 2008 15:01:06 -0800
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. Received on Fri Apr 18 2008 - 18:01:06 CDT