table record distribution query.

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  • Paul Hallam
    #1

    table record distribution query.

    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
    Tags: None
    • Mark D Powell
      #2
      Re: table record distribution query.

      paul_hallam@hot mail.com (Paul Hallam) wrote in message news:<5ed44bd3. 0309030045.71b4 24ff@posting.go ogle.com>...[color=blue]
      > 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[/color]

      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 --

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