MNT$M_OVR_SHAMEM allows you to mount former shadow
set members outside of the shadow set. If you do not specify this
option, $MOUNT automatically mounts the volume write-locked to prevent
accidental deletion of data. To specify this option, you must either
own the volume or have the VOLPRO privilege.
use this option, the shadow set generation number is erased from the
volume. If you then remount the volume in the former shadow set, $MOUNT
considers it an unrelated volume and marks it for a copy operation.