Locks a range of pages in the working set; if the pages are not
    already in the working set, it brings them in and locks them. A
    page locked in the working set does not become a candidate for
    replacement.

    Format

      SYS$LKWSET  inadr ,[retadr] ,[acmode]

    C Prototype

      int sys$lkwset  (struct _va_range *inadr, struct _va_range

                      *retadr, unsigned int acmode);