Deletes a range of addresses from a process's virtual address
    space. Upon successful completion of the service, the deleted
    pages are inaccessible, and references to them cause access
    violations.

    Format

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

    C Prototype

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

                      *retadr, unsigned int acmode);