{
{  The purpose of this request is to open a file for segment
{ access.  The requestor's ring number must be <= osc$tsrv_ring.
{ The type of the pointer returned is specified by the caller.
{
{  dmp$open_file (sfid, ring1, ring2, access_rights, access_selections,
{                 segment_pointer, status)
{
{  sfid: (input) Specifies the file identification for the file to
{                be opened.
{
{  ring1: (input) Specifies the first of two ring numbers to be used in
{                 creating the ring brackets of the file.
{
{  ring2: (input) The second of the two rings.
{
{  access_rights: (input) Specifies what kind of access to the file
{                         the caller requires.
{
{  access_selections: (input) Specifies how the caller wishes to access
{                             the file.
{
{  segment_pointer: (input/output) Specifies the type of pointer to be
{                             constructed.  The pointer is returned in
{                             this parameter.
{
{  status: (output) This parameter returns the result of the request.
{

