{
{   The purpose  of this request is to remove the permanent file root from the
{ master volume set table.  If no permanent  file  root  had  previously  been
{ stored  the  request does not modify the volume set table (and normal status
{ is returned).  If a pf root had been stored it  is  freed  from  the  master
{ volume  set  table,  and  the master volume set table is modified to reflect
{ that the pf root is no longer stored.  This routine attaches  (and  returns)
{ the volume set table (device file).
{
{       STP$PURGE_VST_PF_ROOT (MASTER_VSN, STATUS)
{
{ MASTER_VSN:  (input)  This parameter specifies the name of the master vsn of
{       the set for which the pf root is to  be  removed.   This  is  used  in
{       attaching  the  device  file  (volume  set  table).   This  is assumed
{       correct.
{
{ STATUS: (output) This parameter returns the request status.
{
{       CONDITIONS: ste$attach_df_error
{                   ste$open_error
{                   ste$vol_not_in_set
{
{       IDENTIFIER: stc$set_management_id
{
