VTAPE is externalizing to USS using a NFS server running on a Windows machine.
It can be started without problem and SVTS D USS command can be used to display USS information, but when externalization starts VTAPE is locked by message
SVT1D9920I REFRESH=USS,NOREAD command timed out. Reply W(ait) or C(ancel)
Release : 12.6
Component : CA VTAPE
The problem can be caused by a performance issue between the NFS Client running on z/OS and the NFS Server. Consider Increasing the bandwith between z/OS and the NFS server machine.