Interval=number-seconds
    Nointerval

    Specifies the number of seconds for which the backup process
    waits. Use this qualifier in conjunction with the Continuous
    qualifier and the extensible journaling method. The interval
    determines how often to test the active .aij file to determine
    if it contains more blocks than the value of the Threshold
    qualifier.

    If you specify the Interval qualifier without specifying the
    number of seconds, or if you omit this qualifier, the default
    number of seconds is 60.

    Oracle Corporation recommends using the default (Interval=60)
    initially because the interval that you choose can affect the
    performance of the database. In general, you can arrive at a
    good interval time on a given database only by judgment and
    experimentation.

    If you specify the Nointerval qualifier, the active .aij file is
    tested repeatedly with no interval between finishing one cycle
    and beginning the next.

    You must specify the Continuous qualifier if you specify either
    the Interval or Nointerval qualifier.

    If you specify both the Interval and Nocontinuous qualifiers, the
    Interval qualifier is ignored.