datablock sizing

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  • Vissu
    #1

    datablock sizing

    Hi All,

    Thank you for your feedback on # of tablespaces. Can anyone share some
    experiences on sizing the data block ?.

    Assuming that the biggest row I would have takes up about 2K, what
    should be the size of data block? I am debating between 8K and 16K. Is
    there a rule of thumb as to how many rows should fit in a data block?.

    Thanks a lot in advance,

    Vissu
    Tags: None
    • sybrandb@yahoo.com
      #2
      Re: datablock sizing

      vissuyk@yahoo.c om (Vissu) wrote in message news:<2bedd6a7. 0403041956.3935 854e@posting.go ogle.com>...[color=blue]
      > Hi All,
      >
      > Thank you for your feedback on # of tablespaces. Can anyone share some
      > experiences on sizing the data block ?.
      >
      > Assuming that the biggest row I would have takes up about 2K, what
      > should be the size of data block? I am debating between 8K and 16K. Is
      > there a rule of thumb as to how many rows should fit in a data block?.
      >
      > Thanks a lot in advance,
      >
      > Vissu[/color]

      It really depends on the nature of your application. Oracle will
      always read a block, even if you need a single row. Consequently if
      you run an OLTP app and your blocksize is 16k, and you retrieve only 1
      row, you waste 14k (according to your figures). If 8k you only waste
      6k. If you have a warehouse app, 16k might help you.
      In 9i you can have tablespaces with different blocksizes.

      Sybrand Bakker
      Senior Oracle DBA

        Comment

        • Mark D Powell
          #3
          Re: datablock sizing

          vissuyk@yahoo.c om (Vissu) wrote in message news:<2bedd6a7. 0403041956.3935 854e@posting.go ogle.com>...[color=blue]
          > Hi All,
          >
          > Thank you for your feedback on # of tablespaces. Can anyone share some
          > experiences on sizing the data block ?.
          >
          > Assuming that the biggest row I would have takes up about 2K, what
          > should be the size of data block? I am debating between 8K and 16K. Is
          > there a rule of thumb as to how many rows should fit in a data block?.
          >
          > Thanks a lot in advance,
          >
          > Vissu[/color]

          What kind of application does the database have to support: OLTP, DSS,
          OLAP, etc ...?

          The answer depends of what type of processing is most common, most
          critical etc.... I am in favor of using multiple block sizes in one
          database. To do so means you must manage multiple buffer pools and
          you can easily end up with the condition that during specific
          processing periods you need the memory dedicated to 4K blocks in the
          16K block pool but the 16K block pool is under utilized 85% of the
          time so the space would be better allocated to the 8K pool.

          HTH -- Mark D Powell --

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