RE: Locally managed tablespaces

From: Tim Sawmiller <sawmillert_at_state.mi.us>
Date: Wed, 31 Jan 2001 11:04:59 -0800
Message-ID: <F001.002A60FC.20010131104233@fatcity.com>

505 was the old limit for 8k databases, before the advent of unlimited extents which we have now. for 4k it was 249, 2k was 127....

>>> chuck_hamilton_at_yahoo.com 01/31/01 12:27PM >>>

Where did you get the number 505 from? I read somewhere that 64k is allocated at the beginning of each datafile in a LMT for a bitmap yielding approximately 256k bits for the bitmap per datafile. If each bit represents one extent, I'd expect to be able to have a lot more than 505 extents.
paquette stephane <stephane_paquette_at_yahoo.com> wrote: When using locally managed tablespace, you should not have more extents than the number of extents that the segment header can hold in 1 block.

For a 8K block you should not have more than 505 extents.

The main drawback I see with lmt using uniform extent is if you want to change the extent size. You must drop/recreate the tablespace or migrate it to dictionnary managed ,make the change than migrate it back to locally managed.

Also, If all your tbs are locally managed you must have an online rollback segment in the system tablespace before putting all the other rbs offline (like in Oracle 7.1) .

"Malkuns, Skip" a écrit : > Is anyone using LMTSs? What is the largest number of
> extents that an object
> has?
> Notice any performance difference between LMTS and
> Locally managed
> tablespaces??
> Had any problems with LMTS?
> Skip
>
> > -----Original Message-----
> > From: The Oracle DBA [SMTP:theoracledba_at_lycos.com]
> > Sent: Tuesday, January 30, 2001 2:11 PM
> > To: Multiple recipients of list ORACLE-L
> > Subject: Re: Locally managed tablespaces
> >
> > Has anyone taken a PROD DB and changed it to using
> LMTSs and then noticed
> > a perf change + or -?
> >
> > ---
> >
> > TheOracleDBA
> > theoracledba_at_lycos.com
> >
> >
> >
> > On Tue, 30 Jan 2001 10:30:29
> > Bunyamin K.Karadeniz wrote:
> > > But some had claimed that Locally managed
> tablespaces are slower. I
> > do
> > >not know if it is correct but you must consider
> it .
> > > And I wonder the performance results too.
> > >----- Original Message -----
> > >To: Multiple recipients of list ORACLE-L
>
> > >Sent: Tuesday, January 30, 2001 3:35 PM
> > >
> > >
> > >> I have always been concerned with fragmentation
> of tablespaces, whether
> > it
> > >> be lots of extents, honeycomb or
> > >> bubble fragmentation. Now I am reading that in
> Oracle 8i with the use
> > of
> > >> locally-managed table spaces,
> > >> these concerns are a thing of the past as
> Oracle now uses bit maps
> > within
> > >> the tablespaces themselves to
> > >> do space management. This seems foreign to me
> that even though Oracle
> > will
> > >> use up all the space in
> > >> the tablespaces with no coalescing, it is OK
> that extents will go into
> > >the
> > >> thousands with no performance degradation.
> > >> Could folks who are currently using locally
> managed tablespaces please
> > >> comment on how well it
> > >> is working for them and if they have
> experienced any problems in using
> > >them.
> > >> Thanks
> > >> Skip
> > >> Here is a good white paper on the subject.
> > >>
> http://www.embarcadero.com/news/white_papers.htm
> > >> --
> >
> --
> Please see the official ORACLE-L FAQ:
> http://www.orafaq.com
> --
> Author: Malkuns, Skip
> INET: SMALKUNS_at_SYSTEMS.TEXTRON.com
>
> Fat City Network Services -- (858) 538-5051 FAX:
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Stephane Paquette
DBA Oracle
stephane_paquette_at_yahoo.com

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Author: Tim Sawmiller
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Received on Wed Jan 31 2001 - 13:04:59 CST