On Alpha and Integrity server systems, adds a range of demand-
    zero allocation pages to a process's virtual address space for
    the execution of the current image. The new pages are added at
    the virtual address specified by the caller.

    This service accepts 64-bit addresses.

    Format

      SYS$CRETVA_64  region_id_64 ,start_va_64 ,length_64 ,acmode

                     ,flags ,return_va_64 ,return_length_64

    C Prototype

      int sys$cretva_64  (struct _generic_64 *region_id_64, void

                         *start_va_64, unsigned __int64 length_64,

                         unsigned int acmode, unsigned int flags,

                         void *(*(return_va_64)), unsigned __int64

                         *return_length_64);