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  1. #1
    Join Date
    Apr 2004

    Unanswered: Calculating Extents sizes?/

    Need you help on this issue, can someone out there knows what is the maximun size that I can give the the first Extent and for the second Extent?

    I have a table with this information from oncheck -pt

    Maximum row size 2035
    Number of special columns 6
    Number of keys 2
    Number of extents 21
    First extent size 1048572
    Next extent size 1048572
    Number of pages allocated 14735940
    Number of pages used 14402144
    Number of data pages 14013018
    Number of rows 26311305

    page size is 2048 or 2KB


  2. #2
    Join Date
    Aug 2003
    Hi gbbatoni,

    The maximun size of extents this is limited by maximun size of your dbspaces.
    Depending on your Ibm-Informix versión can you create large dbspaces or not.
    Now, for calculate of particular table, with the output oncheck -pt, do
    Number of pages allocated 14735940 * your page size = KB.
    Depending on your installation the first and second extent size can be equals or not.


  3. #3
    Join Date
    Dec 2003
    North America

    Extent Sizing

    Hi gbbatoni,

    Anything Gustavo tells you, take it to the bank 'cause he's one this board's gurus.

    I'd like to add-on to his response.

    I calculate the initial extent size for a table experiencing a high level of activity by multiplying # of pages used by page size, then multiply by 1.1 to immediately allow for 10% growth, and divide this value by 1000 to determine the initial extent size because extent sizing is in KB.

    Using your numbers:
    14,402,144 x 2k x 1.1 = 31,684,716,800

    31,684,716,800 / 1000 = 31,684,716 is the initial extent size

    31,684,716 / 10 = 3,168,471 is the next extent size

    The 10% added immediately to allow for growth before you allocate another extent is arbitrary. You could use 5%, 25%, or skip it altogether.

    This method has worked well for me, good luck


  4. #4
    Join Date
    Apr 2004


    Hey thanks
    Sorry I did ot respond before , I was waiting for a e-mail from dbforums
    and I did not receive one.

    Thanks both I will use your advise


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