VMS Help System Services, $SUBSYSTEM, Argument  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 enbflg

    OpenVMS usage:boolean
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    Value specifying whether the protected subsystem identifiers are
    to be saved or restored. If the enbflg argument is set to 0, the
    active subsystem is saved. If it is set to 1, the subsystem is
    restored.