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Thread: What is latch

  1. #1
    Join Date
    Dec 2001
    Posts
    80

    Unanswered: What is latch

    What is the meaning of 'latch' in Oracle, I find from some articles that mention the term 'latch contention', what is it?

  2. #2
    Join Date
    Aug 2004
    Location
    France
    Posts
    754
    Here is the definition of latches :
    Latches

    Latches are simple, low-level serialization mechanisms to protect shared data structures in the system global area (SGA). For example, latches protect the list of users currently accessing the database and protect the data structures describing the blocks in the buffer cache. A server or background process acquires a latch for a very short time while manipulating or looking at one of these structures. The implementation of latches is operating system dependent, particularly in regard to whether and how long a process will wait for a latch.
    Latches inhibit scalability, that's why they have to be minimized. Using bind variables is one of the methods to reduce latches. If you're interested, look for more about bind variables on asktom.

    HTH & Regards,

    RBARAER
    ORA-000TK : No bind variable detected... Shared Pool Alert code 5 - Nuclear query ready .

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