Shared Pool Reserved Space
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Thread: Shared Pool Reserved Space

  1. #1
    Join Date
    Sep 2001
    Posts
    261
    I came across this statement:

    The size of the reserved list, as well as the minimum size of the objects that can be allocated from the reserved list is controlled by the initialization parameter SHARED_POOL_RESERVED_SIZE.

    My question is - How does SHARED_POOL_RESERVED_SIZE parameter control the minimum size of the objects that can be allocated ?

    BTW, must Oracle find contiguous memory space in order to assign a large object? And if large objects takes up continuous space in the shared pool, how does this cause fragmentation?

    I hope you guys can clarify things for me. Thanks a lot!
    The Maverick
    Oracle Certified DBA - 8i

  2. #2
    Join Date
    Jun 2001
    Location
    Helsinki. Finland
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    In release 7.3, Oracle introduced paged PL/SQL. Since then, most of the memory chunks in the shared pool are less then (about) 5K. Thus it would not be very wise to search the shared pool free list and LRU lists for chunks more than 5K. Oracle does not do that any more, Oracle uses namely the shared_pool_reserved_size for those lrage chunks.

    There is a way to encrease 5000 bytes to a bit more (with _SHARED_POOL_RESERVED_MIN_ALLOC) but you should not do that.

    I personally keep a reatio of about 1:10 for shared_pool_size and then shared_pool_reserved_size. 1:20 is the default.
    Oracle Certified Master
    Oracle Certified Professional 6i,8i,9i,10g,11g
    email: ocp_9i@yahoo.com

  3. #3
    Join Date
    Sep 2001
    Posts
    261
    Tuning Reserved Space from the Shared Pool

    "On busy systems, the database may have difficulty finding a contiguous piece of memory to satisfy a large request for memory. This search may disrupt the behavior of the shared pool, leading to fragmentation and poor performance."

    based on OTN - Oracle8i Designing and Tuning for Performance

    How does LARGE PL/SQL objects cause fragmentation in the Shared Pool?


    [Edited by D Maverick on 04-14-2002 at 09:33 PM]
    The Maverick
    Oracle Certified DBA - 8i

  4. #4
    Join Date
    Jun 2000
    Location
    Madrid, Spain
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    7,448
    well I dont think large pl/sql cause fragmentation the problem with large pl/sql objects is they require a larger chunk of free memory in shared pool and in a fragmentated shared pool this is even harder (the reason leads to poor performance) and in fact this in many times are causes of ORA-04031, if you check Metalink one of the solutions for 4031 errors is by increasing the reserved shared pool size and tune the minimum allocation object size so the large objects can be allocated more efficnetly and faster

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