clusterratio

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  • Jo
    #1

    clusterratio

    Hi,
    Could someone pls help me understand what factors might effect the
    clusterratio of an index.What action might increase this value in
    syscat.indexes for a particular index.
    Thanks a lot.

    Tags: None
    • db2admin
      #2
      Re: clusterratio

      cluster ratio get affected when you are deleting and inserting lots of
      data in table.
      it is the alignment of column data in index in accordance with sort
      order of table column
      only one index among many indexes on single table can have 100%
      cluster ratio
      REORG will help you bring up cluster ratio

      RUNSTATS first
      REOGR and then
      RUNSTATS again


      On Mar 2, 11:53 am, "Jo" <joshuajosep... @yahoo.comwrote :
      Hi,
      Could someone pls help me understand what factors might effect the
      clusterratio of an index.What action might increase this value in
      syscat.indexes for a particular index.
      Thanks a lot.

        Comment

        • Mark A
          #3
          Re: clusterratio

          On Mar 2, 11:57 am, "db2admin" <jag...@gmail.c omwrote:
          cluster ratio get affected when you are deleting and inserting lots of
          data in table.
          it is the alignment of column data in index in accordance with sort
          order of table column
          only one index among many indexes on single table can have 100%
          cluster ratio
          REORG will help you bring up cluster ratio
          >
          RUNSTATS first
          REOGR and then
          RUNSTATS again
          It is possible for more than one index to have a cluster ratio of 100,
          but it would be somewhat coincidental.

          For example suppose you had a clustered index on the primary key,
          which was vendor number (defined as an identity column), and another
          indexed column (not clustered) which is the timestamp of when the row
          is inserted (current_timest amp). Then both of these indexes could
          easily have a cluster ratio of 100 (percent).

            Comment

            • Jo
              #4
              Re: clusterratio

              pls let me provide more details. i have 2 identical tables with
              identical data. the only difference is the length of 2 char columns is
              defined longer in one table (table a) than in the other( table b).
              This seems to increase the clusterratio of the index on table a as
              compared to that of on table b. i'm trying to understand how the
              column length affects clusterratio.
              thanks a lot.

                Comment

                • Mark A
                  #5
                  Re: clusterratio

                  "Jo" <joshuajoseph05 @yahoo.comwrote in message
                  news:1173111327 .337124.256830@ 8g2000cwh.googl egroups.com...
                  pls let me provide more details. i have 2 identical tables with
                  identical data. the only difference is the length of 2 char columns is
                  defined longer in one table (table a) than in the other( table b).
                  This seems to increase the clusterratio of the index on table a as
                  compared to that of on table b. i'm trying to understand how the
                  column length affects clusterratio.
                  thanks a lot.
                  Reorg the tables and specify the clustering index as the index to use for
                  the reorg.

                  Execute runstats on the tables, use indexes all, and capture detailed index
                  stats.

                  Now check the cluster ratio.


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