Release 12.1 of NetMaster does not allow for modules used by third party product to be placed in the CC2DLINK library that can then be placed in the system linklist, or used as a STEPLIB for the third-party product. This creates a small exposure where the wrong module may be loaded.
This has been addressed in release 12.2.
We made that change in two fixes - RO93965 and RO93966 - for release 12.2 so that you would find NMCDSTEX and the module that it calls, NM000FCX, in CC2DLINK. This library is still an SMP target library though so maintenance would impact it if the modules were changed - as you would want.
If you have a custom exit NMCDSTEX, I have some suggestions to avoid it being over-written.
1. Create a small load library and place it last in the Connect:Direct STEPLIB concatenation. You would link-edit your NMCDSTEX into that library and you would need to copy NM000FCX. The only downside is that if there is any maintenance to either of these, it would not be applied, but in the case of NMCDSTEX, you would not want it to be applied except by re-assembly of the exit.
2. Link edit your exit and give it a different name, change the name in the Connect:Direct parameters to match, and you would be safe from having it over-written. No modules in CC2DLOAD start with "CD" so you could use that.