Note 35272.1 hasn't been replaced yet.....
"Connor McDonald" <connor_mcdonald_at_yahoo.com> wrote in message
news:3ED22AF4.155E_at_yahoo.com...
> Howard J. Rogers wrote:
> >
> > No. Let's be clear:
> >
> > The rule-based optimizer goes in 10i (though support in various forms
> > continues). Therefore, you are still supposed to use rule-based on the
data
> > dictionary in 9i.
> >
> > No doubt some sort of pre-10i migration to the CBO has been made in 9i,
> > which is probably why it isn't so painful to make the switch as it was
in
> > earlier versions. They aren't going to unleash a CBO-accessed dictionary
on
> > an unsuspecting world (without having tested it on an unsuspecting 9i
> > world).
> >
> > In a similar way, if Dictionary Managed Tablespace is disappearing in
10i,
> > or 11i, it makes sense to switch to an LMT SYSTEM tablespace a bit
earlier
> > than that so the bugs can be ironed out before no-one has a choice in
the
> > matter.
> >
> > But a CBO SYSTEM tablespace still isn't recommended in 9i.
> >
> > Will it do harm? Probably.
> >
> > Will it do the sort of harm that you would have experienced in 8.0 or
8i?
> > Probably not: a lot of the code that 10i will contain must have already
> > crept into 9i (version 2, at any rate).
> >
> > Regards
> > HJR
> >
> > "Ryan" <rgaffuri_at_cox.net> wrote in message
> > news:cB8Aa.97348$823.47068_at_news1.east.cox.net...
> > >
> > > "Jack Silvey" <depifster_at_yahoo.com> wrote in message
> > > news:25c7944d.0305251049.4b6064fc_at_posting.google.com...
> > > > Ryan,
> > > >
> > > > Without stats on the DD, your recursive data dictionary queries run
> > > > under rule based optimization, which is the intent in earlier
versions
> > > > of Oracle (<9i).
> > > >
> > > > If you analyze the DD, the optimizer will try to use cost based
> > > > optimization in dictionary queries. This can be a disaster since the
> > > > dictionary was designed long ago to run under rule. The CBO could
> > > > start making very bad choices about execution plans and this can
> > > > really slow down all your users (sort segment allocation, query
> > > > parsing, space allocation, stats gathering, etc.)
> > > >
> > > > A good thing might be to test on your dev/qa systems.
> > > >
> > > > hth,
> > > >
> > > > Jack Silvey
> > > > warehouse DBA somewhere in Texas
> > > >
> > > >
> > > >
> > > > > acceptable? does it help at all or its just not a bad thing?
> > >
> > > pre-9i? Wait a second, everything I have read and seen has said that
9i
> > > still uses the RBO on the system tablespace? Its not until version 10
that
> > > the CBO will be used on the data dictionary.
> > >
> > > Or have I been reading the wrong material?
> > >
> > >
>
> I'm sure there's a metalink note that somewhat contradicts this - along
> the lines that in 9.2 cbo stats on the dictionary is fully supported.
> The only issue is deciding whether 'supported' = 'advantageous'
>
> hth
> connor
> --
> =========================
> Connor McDonald
> http://www.oracledba.co.uk
>
> "Some days you're the pigeon, some days you're the statue"
Received on Mon May 26 2003 - 11:58:24 CDT
