Re: Experts only: Extent sizes

schluete_at_deneb.informatik.uni-hannover.de (Axel Schlueter) wrote:

> whenever I try to create a table with INITIAL = 16K, Oracle allocates extents
> with 20K. My blocksize is 2K, I got this behaviour on ORACLE 7.1.3 and 7.3.2.
 

> As far as I see, Oracle always allocates multiples of 5 Blocks, but I haven't
> found anything in Oracle's documentation or white papers.
 

> Any suggestions?

I remember being told about this on Oracle's DBA course. AFAIR, the INITIAL extent will always be a minimum of 10 blocks, but NEXT and subsequent extents can be any multiple (including 1) of your blocksize. That's if I remember it right!

So if you do INITIAL 1K NEXT 1K and force the segment to extend, you'll use 22K of space; 20K (10 blocks) initially and then 2K (1 block) as a next extent.

Yep, it's a feature - it's probably documented *somewhere* but I couldn't tell you where!!

Cheers,

Pete

--
Peter Moore.
DBA, IS Ops,
Sequent Computer Systems Ltd, Weybridge, UK.