/sys$common/syshlp/helplib.hlb DUMP, Parameter  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 filespec [,...]

    Specifies the file or name of the device being dumped.

    If the specified device is not a disk, a tape, or a network
    device, or if the device is mounted with the /FOREIGN qualifier,
    the file specification must contain only the device name.

    If the specified device is a network device, a disk device, or a
    tape device that is mounted without the /FOREIGN qualifier, the
    file specification can contain the asterisk (*)  and the percent
    sign (%) wildcard characters.

    Files-11 C/D format standards have been implemented on mounted
    and foreign mounted volumes.