TNS-01194
After adding SECURE_REGISTER_LISTENER to the listener.ora to prevent TNS Listener remote poisoning, we found TNS-01194 in the listener log of the server.
Let's check what we can see in the listener's log.
[oracle@db1 ~]$ tail -f $ORACLE_BASE/diag/tnslsnr/$(hostname -s)/listener/trace/listener.log
...
Mon JUL 30 15:01:34 2018
30-JUL-2018 15:01:34 * service_update * ORCL1 * 0
30-JUL-2018 15:01:43 * service_register_NSGR * 1194
TNS-01194: The listener command did not arrive in a secure transport
Mon JUL 30 15:02:04 2018
30-JUL-2018 15:02:04 * service_update * ORCL1 * 0
Mon JUL 30 15:02:34 2018
30-JUL-2018 15:02:34 * service_update * ORCL1 * 0
30-JUL-2018 15:02:43 * service_register_NSGR * 1194
TNS-01194: The listener command did not arrive in a secure transport
Mon JUL 30 15:03:01 2018
30-JUL-2018 15:03:01 * service_update * ORCL1 * 0
Mon JUL 30 15:03:31 2018
30-JUL-2018 15:03:31 * service_update * ORCL1 * 0
Mon JUL 30 15:03:43 2018
30-JUL-2018 15:03:43 * service_register_NSGR * 1194
TNS-01194: The listener command did not arrive in a secure transport
In the log, we found "TNS-01194: The listener command did not arrive in a secure transport". Which means a remote instance tried to register services with the listener every 60 seconds but failed eventually.
The error tells us that Class of Secure Transports (COST) is actually taking effect, we don't have to worry about it. Next, we should trace the remote instance and take any proper action to resolve TNS-01194.