VMS Help SET, VOLUME, Qualifiers, /LABEL  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /LABEL=volume-label

    Specifies a 1- to 12-character ANSI name to be encoded on the
    volume. The specified label remains in effect until it is changed
    explicitly; dismounting the volume does not affect the label.
    Compaq strongly recommends that a volume label should consist
    only of alphanumeric characters, dollar signs ($),  underscores
    (_),  and hyphens (-).

    If you change the volume label on an OpenVMS system disk, you
    should also update the POLYCENTER Software Installation utility
    database. To accomplish this, use the PRODUCT REGISTER VOLUME
    command to replace the old volume label with the new volume
    label.

                                   NOTE

       Changing the volume label does not change other structures
       that used the original volume label. For example, the
       DISK$labelname logical is not changed nor is the device-lock
       name that is kept internally by OpenVMS. As a result, if
       you attempt to access another disk that has the same volume
       label as the original volume of this device, you may get
       error messages such as the following: "%MOUNT-F-VOLALRMNT,
       another volume of same label already mounted".

       Compaq recommends that, if you change a disk volume label,
       you also dismount and remount the disk on all nodes in the
       cluster so that the names and locks are consistent.