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Thread: CLOB disk space

  1. #1
    Join Date
    Jan 2003
    Posts
    34

    Thumbs down Unanswered: CLOB disk space

    Hi,

    I have a little problem .
    If a field of a table is defined as CLOB,how many disk space
    is used by ORACLE?
    Help me, please and excuse my english.

    Thank you in advance

  2. #2
    Join Date
    Sep 2003
    Location
    Virginia, USA
    Posts
    246
    In general, an empty CLOB uses 1 extent, which is 64K on most new databases.

    To understand why this is, recall the fact that each CLOB is an additional segment of an existing table. For example, a table with 2 CLOB columns has 3 segments: one for all non-CLOB columns, and two for your CLOBs.

    Each new segment uses the storage properties of the tablespace, unless you specify segment storage parameters. In my case, my application tablespaces are locally managed with autoallocate, so all of my CLOB segments start with 1 extent that is 64 KB. You might have completely different results.

    Query the view USER_SEGMENTS to find the names of your CLOB segments. For example, SELECT SEGMENT_NAME FROM USER_SEGMENTS WHERE SEGMENT_TYPE = 'LOBSEGMENT';

    The names can be ugly system-generated names like SYS_LOB0000045854C00004$$. Then, run the query like this example:

    SELECT BYTES, EXTENTS, INITIAL_EXTENT, NEXT_EXTENT
    FROM USER_SEGMENTS
    WHERE SEGMENT_NAME = 'SYS_LOB0000045854C00004$$';
    MarkRem
    Author, Oracle Database 10g: From Nuts to Soup
    http://www.remidata.com/book_nuts2soup.htm

  3. #3
    Join Date
    Jan 2003
    Posts
    34

    thank you

    Thank you mark.

    I will try your advices.

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