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  1. #1
    Join Date
    Jul 2001
    Location
    Rotterdam, NL
    Posts
    1

    Unanswered: Does Oracle include COMPRESSION?

    I wonder if the Oracle DB products (and other DB products as well) include compression facilities.

    I guess they don't and that compression is only used for historical / admin backups, i.e. offline tape or optical backups.

    Is that right?

    If not, does anyone have contacts at Oracle I can talk to?

    I'd like to kow how they choose a compression solution.

    Thanks!

  2. #2
    Join Date
    Feb 2001
    Location
    NC, USA
    Posts
    200
    As far as I know, Oracle does not offer anything like that. I guess thyey assume that if you can afford Oracle, you can afford disk space

    Just for a laugh, I tried creating a datafile on an NT compressed drive... Oracle could not access it.

  3. #3
    Join Date
    Apr 2003
    Posts
    9

    Re: Does Oracle include COMPRESSION?

    Hi

    You can use oracle compression utilty for compressing indexes.

    alter index <index name > rebuild compress;


    This can save you disk space and performance gain when using index range scan.

    Mangesh

  4. #4
    Join Date
    Feb 2001
    Location
    NC, USA
    Posts
    200
    Since this thread was started, Oracle 9i Release 2 was made available which also supports data segment compression:

    Code:
    CREATE TABLE table_t$a1 COMPRESS AS 
       SELECT * FROM table_t
    /
    ~~~~~~~~~
    Oracle9i Release 2 (9.2) achieves a good compression ratio in many cases with no special tuning. However, if you need a better compression ratio, tuning can improve it slightly in some cases and very substantially in other cases.

    Heap-organized block-level compression works by eliminating column value repetitions within individual blocks. This is done by moving such repeated column values into a shared block-level symbol table and replacing occurrences with references into the symbol table. Therefore, the compression ratio is higher in blocks that have more repeated values. As a database administrator or application developer, you can take advantage of this fact by reorganizing rows in the segments that you want to compress, to increase the likelihood of such repetitions.

    ~~~~~~~~~

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