VMS Help Sys Parameters, BREAKPOINTS  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    If XDELTA is loaded, BREAKPOINTS enables additional built-in
    calls for XDELTA during the boot sequence. The breakpoints that
    are enabled may change from release to release of OpenVMS.

    This special parameter is used by Compaq and is subject to
    change. Do not change this parameter unless Compaq recommends
    that you do so.