On May 13, 7:58 pm, Mark D Powell <Mark.Pow..._at_eds.com> wrote:
> On May 13, 5:36 pm, sybra..._at_hccnet.nl wrote:
>
>
>
>
>
> > On Sun, 13 May 2007 17:07:21 -0500, "Dereck L. Dietz"
>
> > <diet..._at_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 -
>
> > - Show 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 -
>
> - Show quoted text -
In addition to the above, 7MB of data is "nothing" for an Oracle
database regardless of the version and physical capabilities of the
machine (supposing it is not run on a 286 pc), unless tedious requests
are made.
Received on Mon May 14 2007 - 09:29:48 CDT
