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  1. #1
    Join Date
    Jun 2008
    Posts
    40

    Unanswered: significance of blocking cursor in application snapshot

    Hi ,
    can any one tell me what is the significance of the entry 'blocking cursor =yes' in the application snapshot

  2. #2
    Join Date
    May 2003
    Location
    USA
    Posts
    5,737
    Blocking is good in terms of performance. That means that rows are physically transmitted to the client in blocks instead of one row at a time (even though the client program processes the cursor logically one row at time). There are certain types of updatable cursors that cannot be transmitted to the client in blocks for data integrity reasons.
    M. A. Feldman
    IBM Certified DBA on DB2 for Linux, UNIX, and Windows
    IBM Certified DBA on DB2 for z/OS and OS/390

  3. #3
    Join Date
    Jun 2008
    Posts
    40
    Quote Originally Posted by Marcus_A
    Blocking is good in terms of performance. That means that rows are physically transmitted to the client in blocks instead of one row at a time (even though the client program processes the cursor logically one row at time). There are certain types of updatable cursors that cannot be transmitted to the client in blocks for data integrity reasons.
    thanks for the reply

    In my snapshot i see only couple of blocking cursors =yes and rest of them as no . is it good or bad ? also for all blocking cursor no the stmt type is static. so is it that for all static stmt the blocking cursor is no

  4. #4
    Join Date
    Jan 2007
    Location
    Jena, Germany
    Posts
    2,721
    As Markus_a said, it is good if most (if not all) statements use blocking cursors. If your situation is good or bad is hard to tell. If all the "no"s are statements for updatable cursors, you may not be able to change anything about it. Otherwise, you may want to see if the statements use the FOR UPDATE clause or FOR READ ONLY (I don't know what the default is), for example. You should also verify how much heap is available for the blocked result set. And have a look at the access plans for the "no" statements as well.

    p.s: Cursor blocking has nothing to do with static vs. dynamic SQL (assuming properly written statements).
    Knut Stolze
    IBM DB2 Analytics Accelerator
    IBM Germany Research & Development

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