Hi Vijakumar,
As you are seeing the correct server trancode being called from the IEFMCN.LOG then the trancode routing from the client to the Client Manager would seem to be working correctly i.e. either the default to use Client Manager from generation time is being picked up ("Communications="Gen") or you have "<TRANCODE> CM" set in the commcfg.ini file.
If the Client Manager is configured to connect to CICS Socket Listener then the connection should be non-persistent so IEFMCN.LOG should show "Non-Persistent socket connection" and a different local socket id will be used for every transaction execution: TCP/IP Socket Connections - CA Gen - 8.5 - CA Technologies Documentation
Therefore at this stage it seems the problem root cause is at the CICS server end.
Assuming the Client Manager is only configured for the 1 CICS Socket Listener for all transactions i.e. existing transaction which is working and new transaction which is not working, is it possible the trancode for the new transaction has not been correctly defined to the CICS region?
Regards,
Lynn