I hate passing the buck on an explanation but I don't want to explain it
incorrectly. This site does a good job of describing it
http://www.dbasupport.com/oracle/ora9i/CBO7_1.shtml but I would go to the
Oracle documentation for the accurate way to implement it. I do want to say
that one problem we've run into a few times is that if you give someone a
hammer, everything looks like a nail. It happened to us a few years ago
when we fixed a problem with an index, the customer was wanting to create
indexes for everything. Now we seem to have an exponential grown in
outlines.
On 3/9/06, Nuno Souto <dbvision_at_iinet.net.au> wrote:
>
> genegurevich_at_discoverfinancial.com said,on my timestamp of 10/03/2006 1:12
> AM:
>
> > disabled a PK on one of the tables. I can't modify the SQL in any way
> > because it is generated by
> > a reporting tool (Cognos) it won't add hints or +0 etc.
>
> Don't you just love that? :(
>
> > What I was mostly wondering is whether this situation (PK createing a
> > performance degradation) is a symptom of
> > some other problem which I need to look at.
>
> I don't think so, abstracting any "undocumented features".
> Like Kevin said, stored outlines might be of help here?
> And if it's 10g, we're supposed to be able to hint a
> statement directly in the cache, without need of the source.
> Or at least that's what the white papers would have one
> believe.
>
>
> --
> Cheers
> Nuno Souto
> in sunny Sydney, Australia
> dbvision_at_iinet.net.au
> --
> http://www.freelists.org/webpage/oracle-l
>
>
>
--
http://www.freelists.org/webpage/oracle-l
Received on Thu Mar 09 2006 - 10:00:08 CST
