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Thread: gets and pins

  1. #1
    Join Date
    Oct 2008
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    Chandigarh, India
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    gets and pins

    i have an issue understanding gets and pins:
    below is a query:
    SQL> select NAMESPACE,GETS,GETHITS,PINS,PINHITS from v$librarycache;

    NAMESPACE GETS GETHITS PINS PINHITS
    --------------- ---------- ---------- ---------- ----------
    SQL AREA 81863 80776 273732 272261
    TABLE/PROCEDURE 78744 77553 80318 77782
    BODY 648 619 652 611
    TRIGGER 1005 993 1005 993
    INDEX 22479 22393 22404 22318
    CLUSTER 404 395 566 554
    OBJECT 0 0 0 0
    PIPE 0 0 0 0
    JAVA SOURCE 0 0 0 0
    JAVA RESOURCE 0 0 0 0
    JAVA DATA 0 0 0 0

    11 rows selected.

    gets is number of lookups for objects of the namespace.
    pins is number of reads or executions of objects of namespace.

    My doubts are:
    1. wenever executions takes place, a lookup will be performed whether object is in library cache. If it is so, then pins shud be equal to gets.But pins is larger than gets???
    2. If i believe dat gets means only the number of lookups for new objects...Then what is the meaning of gethits??
    lucky

  2. #2
    Join Date
    Nov 2002
    Location
    Mooresville, NC
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    Gets: Number of time request made (May be 100 time for example)
    GETHITS: Number of time it found in memory ( may be 98 out of 100 time requests)
    PINS: Number of times PIN requested. Remember PIN is Object is being Kept in memory PLUS Use a previously loaded object which already in memory. If it does not find in memory a RELOADS happens.
    Last edited by malay_biswal; 03-09-2009 at 01:36 AM.
    http://www.perf-engg.com
    A performance engineering forum

  3. #3
    Join Date
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    Quote Originally Posted by malay_biswal View Post
    PINS: Number of times PIN requested. Remember PIN is Object is being Kept in memory PLUS Use a previously loaded object which already in memory. If it does not find in memory a RELOADS happens.
    So, it means execution of query requires various objects out of which some may be loaded by this query(or already loaded) and some were loaded by sm other query's execution, in d past, n these will be used by the objects of this query or by this query..
    lucky

  4. #4
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    Yes.
    http://www.perf-engg.com
    A performance engineering forum

  5. #5
    Join Date
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    thanks
    lucky

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