> > On Sun, 13 May 2007 17:07:21 -0500, "Dereck L. Dietz"

> > <diet@ameritech.net> wrote:
> > >I've been reading and came across a section about the impact of table extent
> > >size on performance.

> > >I'd like to apply what I read but before I go off and do it wrong I thought
> > >I'd post what I'm considering and see what observations/comments/suggestions
> > >anybody would like to share.

> > >Basic assumptions:

> > >1.    Operating system I/O buffer size is 128K.
> > >2.    NEXT extent size will be 128K.
> > >3.    During table loads/reloads the table size will not grow to where it
> > >needs more than one more extent.
> > >4.    The table's initial size will be 55,433 rows for a current size of
> > >7,737,465 bytes.
> > >5.    Datawarehouse environment.  No real data design/normalization.
> > >6.    Oracle 10.2.03, Windows 2003 Server, 16GB memory.

> > >When I initially create the table, what would be the best option:

> > >1.    Create it with an initial extent of 7,737,465 bytes allocating all the
> > >space it needs at once.

> > >2.    Create it with an initial extent as a multiple of 128K but large
> > >enough to hold the initial rows.

> > >3.    Just create it with an initial extent of 128K.

> > The best option would be
> > 1 forget about this old myth
> > 2 In a LMT: just create the table and stop worrying. Your extent
> > clause will be recalculated in terms of tablespace extent sizes
> > automagically anyway.
> > 3 Consider migrating to a real operating system.

> > --
> > Sybrand Bakker
> > Senior Oracle DBA- Hide quoted text -

> >

> Dereck, table and index sizing decisions as to number and size of
> extents pretty much have to be made only for objects stored in
> dictionary managed tablespaces.  Since Oracle introduced Locally
> managed tablespaces the number and size of extents is determined by
> the database for you based on the tablespace definition.

> Locally managed tablespace extent allocation is fully explained in the
> Concepts and DBA Administration manuals.  All your tablespaces should
> be using local managment.

> HTH -- Mark D Powell --- Hide quoted text -

>