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FW: Different flavors of relational database

  • 1.  FW: Different flavors of relational database

    Posted 05-02-2006 08:01 AM
    Kay,
    One reason you may see this is that a relational database does a table
    scan only across the pages that contain the table rows (it keeps track
    of this stuff).
    IDMS does not know that instances of record X are only on pages 4, 12,
    28, and 56. It must examine every page of the area looking for
    instances. So if you put record X in the same area as records A, B, and
    C and the area is 10,000 pages, then IDMS reads 10,000 pages while SQL
    reads 4 pages (4, 12, 28, and 56).

    If you were to put each record in its own private area (or sub-area)
    with just enough pages to hold the number of records you area loading,
    then you would see comparable timings.


    Richard S. Kenney

    rkenney@lnc.com

    207-842-9658


  • 2.  Re:FW: Different flavors of relational database

    Posted 05-02-2006 08:01 AM
    Kay,
    One reason you may see this is that a relational database does a table
    scan only across the pages that contain the table rows (it keeps track
    of this stuff).
    IDMS does not know that instances of record X are only on pages 4, 12,
    28, and 56. It must examine every page of the area looking for
    instances. So if you put record X in the same area as records A, B, and
    C and the area is 10,000 pages, then IDMS reads 10,000 pages while SQL
    reads 4 pages (4, 12, 28, and 56).

    If you were to put each record in its own private area (or sub-area)
    with just enough pages to hold the number of records you area loading,
    then you would see comparable timings.


    Richard S. Kenney

    rkenney@lnc.com

    207-842-9658