
{
{ The purpose of this request is to change the volume serial number
{ on the current tape subfile if their currently is no active subfile,
{ and the tape_assignment_operations indicates an initial tape,
{ If the operations indicates advance, then it changes the volume serial
{ number of the next tape subfile.  If the operations indicates extend
{ and the volume list is exhausted, it appends another volume
{ on the end of the list.
{
{ This routine follows the same logic as does dmp$select_tape_subfile.
{
{     DMP$UPDATE_TAPE_VSN_LIST (SFID, VOLUME_DESCRIPTOR,
{       TAPE_ASSIGNMENT_OPERATION, STATUS)
{
{ SFID: This parameter specifies the system file identifier of the file
{       whoose vsn list you wish to change.
{
{ VOLUME_DESCRIPTOR: This parameter specifies the new description of the
{       volume.
{
{ TAPE_ASSIGNMENT_OPERATION: This parameter specifies what type of update
{       is allowed.
{
{ STATUS: This parameter specifies the request status.
{
