/HIGHWATER (default)
       /NOHIGHWATER

    Applies to Files-11 On-Disk Structure Level 2 (ODS-2) and Level 5
    (ODS-5) disks only.

    Sets the file high-water mark (FHM) volume attribute, which
    guarantees that users cannot read data that they have not
    written. You cannot specify the /NOHIGHWATER qualifier for
    magnetic tape.

    The /NOHIGHWATER qualifier disables FHM for a disk volume.