VMS Help BACKUP_API, BACKUP$START, Returns  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    OpenVMS usage:COND_VALUE
    type:         longword (unsigned)
    access:       write only
    mechanism:    by value

    Longword condition value. Condition values that this routine can
    return are listed under Condition Values Returned.