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

    (Alpha only) WLKSYSDSK is used by various bootstrap components
    to determine if the system disk should be treated as though it is
    write-locked. This parameter is used primarily to allow OpenVMS
    to boot from a CD.