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Thread: empty_blocks

  1. #1
    Join Date
    Feb 2008
    Posts
    38

    Unanswered: empty_blocks

    Hi
    Does the emty_blocks column in the below query
    show blocks above HWM or empty blocks below HWM


    select table_name,a.blocks,b.bytes/1024 as KB,num_rows,empty_blocks
    from user_tables a, user_segments b
    where a.table_name = b.segment_name
    and empty_blocks >0
    order by empty_blocks desc

    Table_name Blocks KB Num_rows Empty_blocks
    ------------------- --------- ----- ------------ ------------------
    TEMPHISTORY 0 52224 0 6528

  2. #2
    Join Date
    Aug 2003
    Location
    Where the Surf Meets the Turf @Del Mar, CA
    Posts
    7,776
    Provided Answers: 1
    >Does the emty_blocks column in the below query show blocks above HWM or empty blocks below HWM

    No & you should run your own empirical test for obtaining correct answer.

    Create a table.
    Insert a bunch of rows.
    commit;
    delete half the rows.
    run your query.
    You can lead some folks to knowledge, but you can not make them think.
    The average person thinks he's above average!
    For most folks, they don't know, what they don't know.
    Good judgement comes from experience. Experience comes from bad judgement.

  3. #3
    Join Date
    Feb 2008
    Posts
    38
    alter table move clause works for blocks which are only below HWM
    right?

  4. #4
    Join Date
    Aug 2003
    Location
    Where the Surf Meets the Turf @Del Mar, CA
    Posts
    7,776
    Provided Answers: 1
    By definition all data within a table exists below the HWM.
    So there is nothing to move above HWM.

    Why the obsession with HWM; over which you have minimal or no control?

    What SQL is used to obtain HWM for any table?
    You can lead some folks to knowledge, but you can not make them think.
    The average person thinks he's above average!
    For most folks, they don't know, what they don't know.
    Good judgement comes from experience. Experience comes from bad judgement.

  5. #5
    Join Date
    Feb 2008
    Posts
    38
    but
    shrink space command, reclaim space both below and above HWM

  6. #6
    Join Date
    Aug 2003
    Location
    Where the Surf Meets the Turf @Del Mar, CA
    Posts
    7,776
    Provided Answers: 1
    Why the obsession with HWM; over which you have minimal or no control?

    What SQL is used to obtain HWM for any table?

    To what do you use HWM?
    How does HWM relate to any Business Rule?
    You can lead some folks to knowledge, but you can not make them think.
    The average person thinks he's above average!
    For most folks, they don't know, what they don't know.
    Good judgement comes from experience. Experience comes from bad judgement.

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