Re: EXPLAIN PLAN : better with RULE!

Steve Mitchell wrote:
>
> "Jonathan Lewis" <jonathan_at_jlcomp.demon.co.uk> wrote in message
> news:1027158123.29738.1.nnrp-14.9e984b29_at_news.demon.co.uk...
> >
> > Rather than just fiddling with parameters though, the
> > next thing to do is look at the indexes and columns
> > that the RBO has used in its plan, and examine the
> > statistics stored in user_indexes, user_tab_columns,
> > and user_histograms to see why CBO doesn't like
> > them. Also check the stats against the real data
> > to see if the stats are misleading.
> >
>
> Great idea,
>
> Do you know where I might find some reference that would help me
> understand the statistics stored in user_indexes, user_tab_columns, and
> user_histograms? I would like to better understand how these
> fit together to get an idea of why the CBO is ignoring indexes that are
> obviously a better choice.
>
> > --
> > Jonathan Lewis
> > http://www.jlcomp.demon.co.uk
> >
>
> --steve

Once you've toured the manuals, the next logical place is a 10053 trace - which gives the CBO in most of its gorey detail...

hth
connor

-- 
==============================
Connor McDonald

http://www.oracledba.co.uk

"Some days you're the pigeon, some days you're the statue..."