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

    Displays all devices currently allocated to processes.

    If you specify a device name, the characteristics of only that
    device are displayed. If the device is not currently allocated,
    the command displays a message indicating that there is no such
    device. If you specify a generic device name, the characteristics
    of all allocated devices of that type are displayed.