/INTERVAL={delta-time}
       /NOINTERVAL (default)

          Causes a script to execute at regularly scheduled
          intervals. The /INTERVAL qualifier specifies the
          minimum time between two consecutive executions of a
          script.

          Specify time as a delta time. Refer to the VMS DCL
          Concepts Manual for more information on specifying
          times. If you do not specify a time with the
          /INTERVAL qualifier, a default value of 1 day is
          used. This value causes the associated script to run
          every 24 hours.

          If you specify the /AFTER qualifier with the
          /INTERVAL qualifier, the first defragmentation
          operation occurs at or after the time specified
          by the /AFTER qualifier; all subsequent operations
          execute at intervals set according to the /INTERVAL
          qualifier.