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

    (VAX only) LAMAPREGS sets the number of UNIBUS map registers
    allocated to an LPA11 driver when the driver is loaded, and
    limits the registers for the driver to that number. A value of
    0 permits dynamic allocation of an unlimited number of registers.

    LAMAPREGS has the GEN attribute.