Hello,
We are running a 12c (12.1.0.2.0) and a 19c (19.18.0.0.0) databases. We have a client from out of network who connects to 12c and runs queries without issues. Now they requested connection to 19c, we opened the network and we could ping the 19c from the client's network and the tnsping also works. But when we try to connect using sqlplus using ez-connect it is erroring out with “ORA-12541 : TNS: No Listener” message. The same error when using db link or tns names to connect. The telnet also shows that the connection is successful. When we try to connect to 19c using sqlplus from client's machine, we do not see any entry in the listener log in any of the 19c nodes. But we could connect successfully to 19c from other databases within our network, the issue is connecting from the client's network. The network policy is same for both 12c and 19c (same set of rules in the network). Could anyone please point me to the direction where I should look next for to isolate the issue?
Thank you!