This is working as designed.
1. When /PARMS INTERFACES $NM SOCKETS contains IBM as the TCP/IP Software Type, the SYSTCPD DD is required to enable the listener initialization with the TCP/IP stack, so it is allocated as shared.
2. Listeners set up using the USS socket interface do not require the SYSTCPD.
3. If you change the SOCKETS parameter group to use USS and action it, the file remains allocated.
4. However, if you change the SOCKETS parameter group to use USS, save the change (PF4) and cycle the region, the SYSTCPD is not allocated.
The only thing this is changing is the manner in which you set up the listener port with IBM, so it has no adverse effects.
As per item 4 above, change your /PARMS SOCKETS parameter group to use USS, save the change, and cycle the region.
Once that is complete on all involved systems, the TCPIP.DATA will once again be available for update via TSO.
If you have change management that will delay implementation of the above changes, you can update the file within Netmaster:
1.Logon to your Netmaster region and issue /DATASET.
2. Use the EDIT function, putting the DSN of your TCPIP.DATA file in the Dataset Name field and editing the desired TCPIP.DATA from within the Netmaster region.