Re: Is it possible to create a System tablespace with Local managed extent?

You can create rollback segments in a locally managed tablespace. The tablespace must not be autoallocate, i.e set it to a fixed size. You normally put rollbacks in a tablespace dedicated for the purpose, and since they usually all have the same extent size, not using autoallocate will not be an issue.

Kerry

"Howard J. Rogers" <howardjr_at_www.com> wrote in message news:3aa7dc93_at_news.iprimus.com.au...
>
> "andrew_webby at hotmail" <spam_at_no.thanks.com> wrote in message
> news:984063065.26505.0.nnrp-02.c30bdde2_at_news.demon.co.uk...
> > On this note (sort of), I'm trying some experiments just now on a test
> > machine with locally managed tablespaces.
> >
> > I've got them all - except system, obv. - set to either autoallocate or
> > uniform extent as appropriate, but when I tried to create rollback
 segments,
> > it said I couldn't create them in my rbs tablespace... I take it - given
> > sizing of rbs and initial/next/optimum clauses in rbs segment creation -
> > that rbs can't be in locally managed tablespace?
> >
>
>
> This is my favourite 'feature' in 8i!!!!
>
> Read the error message carefully... it should be the one about 'unable to
> use system rollback segment for updates in non-system tablespace'.
>
> The problem is that in order to create a rollback segment in a locally
> managed tablespace, an update has to take place to the bitmap at the start
> of that non-system tablespace to record the extent allocations to the
> segment you're trying to create. That's an *update* to the bitmap.
 Updates
> require rollback. If the update is taking place anywhere other than
 SYSTEM,
> then a non-system rollback segment must be used to house the rollback
> involved.
>
> So it's chicken and egg, catch 22, or whatever other cliche takes your
> fancy: you must have one, non-system rollback segment created in a
> dictionary managed tablespace *before* you can create all your other
> non-system rollback segments in locally managed tablespace. Once you've
> created the first locally-managed rollback segment (and brought it online,
> of course), then all others can be created without hassle -and that first
> one in dictionary managed tablespace can even be dropped.
>
> Incidentally, just to make a lovely story even warmer and fuzzier, that
> first rollback segment can actually be created in the SYSTEM tablespace...
> it's not the tablespace the thing is housed in that determines whether the
> segment is the system rollback segment or not.
>
> Anyway: short answer is that locally managed tablespace makes a proper and
> suitable home for all rollback segments (bar the system one, of course),
 but
> that it takes a bit of a fiddle to make it happen.
>
> Regards
> HJR
>
>
>
>
>
>
>
>
> > In the O8 chapter that explains the concepts of lmt's, this isn't
> > mentioned - though my 'explanation' seems logical enough.
> >
> > (ps. I haven't posted this to all the ng's in case you're wondering..)
> >
> > "Daniel A. Morgan" <dmorgan_at_exesolutions.com> wrote in message
> > news:3AA72736.B43C354A_at_exesolutions.com...
> > > > Is it possible to create a System tablespace with Local managed
 extent?
> > > > Is it better off to have the system tablespace to be dictionary
 managed?
> > >
> > > It is definitely possible. Go to http://otn.oracle.com and enter the
 search
> > > criterion "LOCALLY MANAGED". You will find lots of good reference
 material
> > > on the subject.
> > >
> > > Daniel A. Morgan
> > >
> >
> >
>
>
Received on Thu Mar 08 2001 - 16:13:16 CST