Listener hang issue

Listener fails to process any new connections for some reason multiple listeners start up listening on the same port and running for the same service, this new listener is started by already running listener process which can be checked by looking at the parent process id of the new listener. This issue so far we have seen on and

$ ps -ef | grep tnslsnr

oracle 8909 1 0 Sep 15 ? 902:44 /u01/oracle/db_1/bin/tnslsnr LISTENER
# the parent process id (bold) in the line below is the listener’s process id that started it
oracle 22685 8909 0 14:19:23 ? 0:00 /u01/oracle/db_1/bin/tnslsnr LISTENER

To fix this issue add the following parameter to listener.ora: