pa*********@hotmail.com (Paul Hallam) wrote in message news:<5e**************************@posting.google. com>...
How does oracle distribute records in a table that is in a tablespace
with multiple datafiles.
Very simplisticly Ingres will distribute sequential records evenly
across multiple datafiles for a single table. (Not exact but good
enough for this question.)
How does oracle distribute records for a table that is in a tablespace
with multiple datafiles.
Any pointer to where in the documentation this is explained would also
be appreciated.
Many thanks
Paul
Paul, Oracle distributes rows based on the free list whose membership
is determined by interaction of the table settings for pctfree and
pctused with DML activity. See the Concepts manual for details.
Oracle distributes extents accross the files in a tablespace based on
a whole slew of factors: tablespace space management scheme, free
space availability, next extent size requested, etc....
But if you load an empty tablespace one table at a time you can watch
Oracle stripe the extents for a large enough object accross the files
that make up the tablespace. Oracle does not attempt to rebalance
objects that are unevenly distributed or when new files are added to
the tablespace (as DB2 does).
Once a tablespace is loaded the availability of free space extents
sufficient to hold the requested allocation is the primary driver of
where an extent is allocated in conjuction with the tablespace space
management scheme: uniform extents, autoallocate, or dictionary
managed.
HTH -- Mark D Powell --
