How to make RMAN to use large pool
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Thread: How to make RMAN to use large pool

  1. #1
    Join Date
    Apr 2003
    Location
    Kuala Lumpur
    Posts
    59

    How to make RMAN to use large pool

    I have allocated 32MB for large pool. Whenever RMAN backup runs, I notice higher PGA memory usage. I read in Oracle guide, large pool is used for RMAN. But when I issue 'select * from v$sgastat where pool = 'large pool'', I saw see the free memory is still 32MB. So how can I make use of large pool for RMAN backup operations? What I need to set?

  2. #2
    Join Date
    Nov 2002
    Location
    New Delhi, INDIA
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    1,796
    Amar
    "There is a difference between knowing the path and walking the path."

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  3. #3
    Join Date
    Sep 2001
    Location
    Ohio
    Posts
    334

    Hmmm..

    Amar,
    I read the articles you posted, and thought I'd test it out. My results were not what I expected.

    Large Pool = 80M
    Block Size = 16K
    db_file_direct_io_count = 128
    Files = 9
    Backup_tape_io_slaves = true
    Backing up directly to tape.

    From the first article, my memory usage should be:
    memory(input) = 4 * #files * db_block_size * db_file_direct_io_count
    = 4 * 9 * 16*1024 * 128
    = 72 Meg

    Code:
    SQL> select * from v$sgastat where pool ='large pool';
    
    POOL        NAME                            BYTES
    ----------- -------------------------- ----------
    large pool  free memory                  80000000
    
    SQL> /
    While the backup is running, it only used 278K of the large pool.

    Code:
    POOL        NAME                            BYTES
    ----------- -------------------------- ----------
    large pool  free memory                  79721424
    large pool  KSFQ Buffers                   278576
    What am I missing?

    Thanks!
    Jodie

  4. #4
    Join Date
    Aug 2000
    Posts
    87
    how many channels are using???
    whatz ur filesperset ????

    in general we need to allocated 4 buffers per file.
    each buffer is db_block_size * multi_block_read_count

    for eg:

    db_block_size=8 and multi_block_read_count=8 then 64k per buffer

    64k * 4 * 2(channels)

    This config works fine for me.Rman uses large_pool_size properly

    regards,
    Vinod

  5. #5
    Join Date
    Sep 2001
    Location
    Ohio
    Posts
    334
    Vinod,
    My Filesperset is not set, so it defaults to all my files (9). I am only using 1 channel.

    Also, one of the articles Amar listed had the formula using

    buffersize = db_block_size * multi_block_read_count
    the other had
    buffersize = db_block_size * db_file_direct_io_count

    My multiblock_read_count is 64. With either formula it doesn't appear I am using as much large pool as it says I should.

    Any ideas?

    Jodie

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