Re: Locally Managed Tablespaces - any cons???

"Robert Fazio" <rfazio_at_home.com.nospam> wrote in message news:xNYc7.91101$EP6.22111132_at_news1.rdc2.pa.home.com...
> From what I have read. Oracle doesn't allow for the system tablespace to
 be
> LM. Infact, if you read the docs on dbms_space_admin, you will see that
 it
> won't even allow system to be converted, but the say they will support it
 in
> the future. The other two RBS and TEMP probably shouldn't be either.
 TEMP
> for example is already handled differently if set to type temporary, plus
> you want the ablity to change the extent management at a later time, if
 you
> choose LM, then you can't. RBS has the same issues.
>

I disagree, I'm afraid. Locally managed temp tablespaces are strongly supported and encouraged (indeed, in the 8i DBA course, the syntax example for creating a TEMP tablespace is pure LMT... they don't even mention the old, DMT, way of doing it.

The same is not true for Rollback Segment tablespace, but even there, I'd suggest that they are strongly recommended.

Consider what LMTs are really good at: making massive extent allocation and de-allocation of consistent sizes a trivially easy (and speedy) task. That's a prime requirement for rollback segments, since they have a propensity to grow and shrink all the time. It's also initially true for TEMP tablespace, as the temp segments are created by initial sorts.

The only restriction of RBS tablespace as locally managed is that you must first create a rollback segment in dictionary managed tablespace (any one will do, even SYSTEM) to handle the DML that will take place to the new tablespace's bitmap when you create your first locally managed rollback segment. Once that first LMT rollback segment is online, the starter segment can be offlined and dropped, and all others can be created normally.

Regards
HJR
> Other than some early bugs related to the LM tablespaces, I do agree.
>
> --
> Robert Fazio
> Senior Technical Analyst
> dbabob_at_yahoo.com
>
> "Howard J. Rogers" <howardjr_at_www.com> wrote in message
> news:3b745321_at_usenet.per.paradox.net.au...
> >
> > "Kenneth Koenraadt" <plovmand_at_hotmail.com> wrote in message
> > news:3b7197c5.7098447_at_news.mobilixnet.dk...
> > >
> > > On Tue, 7 Aug 2001 21:20:37 -0600, "Ron Gardiner"
> > > <rongardiner_at_powersurfr.com> wrote:
> > >
> > > >New for 8i (I believe) is locally managed tablespaces...
> > > >
> > > >From what I've read, sounds like there is no reason NOT to use them.
 Can
> > > >they be used for all types of TS?... rollback segs, temporary, how
 about
> > > >system itself?
> > > >
> > > >Any feedback would be appreciated!
> > > >
> > > >
> > > >
> > > Hi Ron,
> > >
> > > You cannot create a locally managed SYSTEM tablespace on database
> > > creation. But you can convert it to LM later with a supplied package.
> > >
> > > The SYSTEM tablespace and the tablespaces for rollback segments must
> > > have the same extent management type, so if you convert the SYSTEM
> > > Tablespace to LMT, rememer to convert your RBS tablespace(s) to LMT as
> > > well.
> > >
> >
> > This is just not true.
> >
> > Firstly, whilst you may be able to convert SYSTEM into a LMT, it's
 strongly
> > advised not to. You may have noticed that SYSTEM also has 50%
 PCTINCREASE,
> > which is generally bad, and is autoextensible, which is also usually
> > considered not terribly efficient... but the point is, SYSTEM breaks all
 the
> > rules, and is best left to do so. LMT/DMT is just another example.
> >
> > Secondly, you appear to suggest that if SYSTEM is DMT, you must have DMT
> > rollback segment tablespace. Absolutely not true. Provided there is
 one
> > non-system rollback segment created (and brought online), you can create
 a
> > LMT rollback tablespace, and create (and online) one LMT'd rollback
> > segment... after which, the original DMT'd rollback segment can be
 dropped,
> > and all others created without a problem. And all of that can be done
> > perfectly well with a SYSTEM tablespace that is merrily chugging a way a
 s
> > dictionary-managed.
> >
> > Incidentally, the SYSTEM tablespace in 9i is still dictionary managed,
 and
> > there is still no provision for creating it Locally Managed... yet
 another
> > indication that locally managed SYSTEM tablespace is not advised, nor
> > necessary.
> >
> > Regards
> > HJR
> >
> >
> >
> >
> > > Regards,
> > > Kenneth Koenraadt
> > > Systems Consultant
> > > Oracle DBA
> > > plovmand@<no-spam>hotmail.com
> >
> >
>
>
Received on Sat Aug 11 2001 - 17:51:54 CDT