RE: Extent allocation

It is a big
clue.  Oracle rounds to multiples of 5 extents to prevent the existence of a free extent of fewer than 5 blocks, which is unlikely to be usable.
 
Paul Baumgartel <FONT face=Tahoma
size=2>InstiPro, Inc. <FONT face=Tahoma size=2>paul.baumgartel_at_instipro.com 212 813-0829 x103 (office) 917
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  size=2>-----Original Message-----From: Yttri, Lisa   [mailto:lisa.yttri_at_cnh.com]Sent: Wednesday, February 07, 2001 4:26   PMTo: Multiple recipients of list ORACLE-LSubject:   Extent allocation
  Hi -
  I am confused now about how oracle actually determines the   size an extent should be.  I have db_block_size set at 8192 and have   defined a tablespace (and tables) at initial and next extents of 128K.    When I do a show parameter db_file_multiblock_read_count it says 8.    Therefore I thought 128K would be a good number, since it is a multiple of   these numbers.
  However, when I check my extent sizes, I see that each extent   contains 10 blocks which is 160K.
  I remember reading an article some time ago about how oracle   actually determines what it thinks the extent size should be.  Does   anyone know of an article like this, or can anyone explain to me why it chose   a different extent size?
  By the way, I looked at several tables and the one common   thing I noticed is that the number of blocks allocated seems to be a multiple   of 5 - ie. some are 5 blocks, some 10, some 20, etc.  I don't know if   that's coincidence or a big clue to the whole thing   Lisa Received on Wed Feb 07 2001 - 15:56:51 CST