The 505 extents for an 8K block size is not the
maximum total extents . It's the maximum performance
wise, in order to read only one block to know where
all extents are.
It is obtain by (db_block_size/16 -7)
So ((8192/16) -7) =505.
This is how many extents location can be store in 1
block in the segment header.
My sources are the document following the document
"How to stop defragmenting and start living" and Steve
Adams web site.
--- Mark Leith <[EMAIL PROTECTED]> a écrit : > I
have an 8k block size on 8.1.6 Win2K system, with
> LMT - UNIFORM extent
> size of 516k and a DEFAULT MAXEXTENTS of 2147483645
> ! This I take it was the
> default, as I didn't specify that on creation.. A
> little more than 505...
>
> Regards
>
> Mark
> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On
> Behalf Of Chuck
> Hamilton
> Sent: Wednesday, January 31, 2001 05:28
> To: Multiple recipients of list ORACLE-L
> Subject: RE: Locally managed tablespaces
>
>
> 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 <[EMAIL PROTECTED]>
> 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
> icrit : > 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:[EMAIL PROTECTED]]
> > > 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
> > > [EMAIL PROTECTED]
> > >
> > >
> > >
> > > 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: [EMAIL PROTECTED]
> >
> > Fat City Network Services -- (858) 538-5051
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> > (858) 538-5051
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>
> =====
> Stephane Paquette
> DBA Oracle
> [EMAIL PROTECTED]
>
>
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