If you know the sizes of all the tables, uniform extents with small,
medium, and large tablespaces is ideal. Small, medium, and large is
generally something like 128k, 4m, 128m, but it really depends on the
application.

If you don't know the size the tables will grow to, autoallocate is
best. Autoallocation will use an internal algorithm to determine the
next extent size. Extents won't be uniform, and the algorithm may
change over time. Currently, you get 16 64k extents, then 63 1m
extents, then 8m extents, etc.

Most storage parameters cannot be overridden at the table level in
LMT's. You cannot specify and INITIAL or NEXT extent size, for example.

Justin Cave
Distributed Database Consulting, Inc.
http://www.ddbcinc.com/askDDBC

-----Original Message-----
From: edwinuy
[mailto:oracledba-ezmlmshield-x12572116.[Email address protected]
Sent: Thursday, January 27, 2005 7:41 PM
To: LazyDBA Discussion
Subject: Sizing the extents - Migrating dictionary to locally managed

Hi all,

Am researching on migrating from dictionary-to-locally managed
tablespaces and am trying to find out how other guys size the extent of
their locally-managed tablespaces.

So far, I've checked out the internet but no one mentioned about how do
you come up with the calculation of what should be your uniform extent
size.

Best practices so far that had been mentioned is to create a SMALL,
MEDIUM and LARGE extent tablespaces, move your tables based on what you
considered should be place in those tablespaces. But there is no mention
of what should be the uniform extent size for the SMALL, MEDIUM and
LARGE. Is it really necessary to work out the uniform extent size or
should I just use AUTOALLOCATE in which case the default is 1MB? In LMT,
the storage parameters of the CREATE TABLEs still overrides the ones on
the tablespace level, right?

Also, the Oracle docs never mentioned about the 64K overhead for the
datafiles, can anyone confirm that you need to add the 64K for each
datafiles that are to be a member of your tablespace. Or is the overhead
supposed to be the database block size, that is, whatever is the value
of DB_BLOCK_SIZE.

Thanks in advance ...






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