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  1. #1
    Join Date
    Aug 2003
    Posts
    123

    Unanswered: multi_file_multiblock_read_count

    What is 'multi block read count', by default in Oracle9i it is 8, can some one help me in understanding what is 'multi block read count' how oracle uses it, advantages and disadvantages of high and low values of multi_block_read_count.


    -Jaggu

  2. #2
    Join Date
    Dec 2003
    Location
    India
    Posts
    33

    Arrow Re: multi_file_multiblock_read_count

    multi_file_multiblock_read_count is the parameter that controls the number of blocks that are read asynchronously in full-table scan operations...
    Papps...

  3. #3
    Join Date
    Aug 2003
    Posts
    123
    well, if the multiblock read count is 100, is it means is that it will read 100 blcok at a time. what is the maximum and the minimum values for this

  4. #4
    Join Date
    Sep 2003
    Location
    Columbia, MD USA
    Posts
    95
    generally, this parameter should be set so that the value you set here x the block size is equal to the the amount of data the system can pull with one request from the disk system

    8 is generally fine for Windows if you have an 8K block size as that is 64K

    if you have a different platform or block size you will want to set it to a different value for the most benefit... your storage setup (stripe size, etc.) can also factor into this...
    Last edited by drew; 12-19-03 at 09:32.
    drew
    ------------------
    http://wjtechnologies.com

  5. #5
    Join Date
    Apr 2003
    Location
    Greenville, SC (USA)
    Posts
    1,155
    By setting this parameter too high, you can cause Oracle to do more
    table scans than it index reads.... The optimizer may believe that it can get to the data quicker than full scan on a table as opposed to using the indexes that it should

    HTH
    Gregg

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