Prefix_Collection=option

    When you convert a database to release 7.2 from a release
    of Oracle Rdb prior to release 7.0, you can use the Prefix_
    Collection qualifier to specify that sorted index prefix
    cardinality collection be Enabled, Enabled Full, or Disabled
    for all sysem and user sorted indexes.

    The following options are available for use with the Prefix_
    Collection qualifier:

    o  Disabled

       Specifies that index prefix cardinality collection is to be
       disabled.

    o  Enabled

       Specifies that default collection is performed. The Oracle
       Rdb optimizer collects approximate cardinality values for the
       index columns to help in future query optimization.

       Enabled Estimate

       Specifies that prefix cardinality values for all indexes are
       to be estimated.

    o  Enabled Collect

       Specifies that prefix cardinality values for all indexes are
       to be collected by calling the RMU Collect command.

    o  Full Requests that extra I/O be performed, if required, to
       ensure that the cardinality values reflect the key value
       changes of adjacent index nodes.

    o  Full=Estimate

       Specifies that prefix cardinality values for all indexes are
       to be estimated.

    o  Full=Collect

       Specifies that prefix cardinality values for all indexes are
       to be collected by calling the RMU Collect command.