On Alpha and Integrity server systems, allows a process to change
    the protection on a page or range of pages.

    This service accepts 64-bit addresses.

    Format

      SYS$SETPRT_64  start_va_64 ,length_64 ,acmode ,prot

                     ,return_va_64 ,return_length_64 ,return_prot_64

    C Prototype

      int sys$setprt_64  (void *start_va_64, unsigned __int64

                         length_64, unsigned int acmode, unsigned

                         int prot, void *(*(return_va_64)), unsigned

                         __int64 *return_length_64, unsigned int

                         *return_prot_64);