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

          The /INTERVAL qualifier 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 one 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.