Review this information for listener migration from earlier database releases.

If your system has an Oracle Database 11g Release 2 (11.2), 12c Release 1 (12.1), or 12c Release 2 (12.2) installation, and you install Oracle Database 18c either to coexist with or to upgrade the Oracle Database 11.2, 12.1, or 12.2 installation, then most installation types automatically migrate the existing Oracle Database listener to the 18c Oracle home. During migration, the upgrade process configures and starts a default Oracle Net Listener using the same TCP/IP port as the existing listener, with the IPC key value.

During the Oracle Clusterware upgrade, the default listener (LISTENER_nodename) is migrated to the Oracle Grid Infrastructure home (Grid home). Oracle Database Configuration Assistant always uses the default listener.

The listener migration process stops the listener in the existing Oracle home, and restarts it in the new Oracle home. If the database was using the default listener (LISTENER_nodename), then Oracle Net Configuration Assistant (NETCA) migrates the listener automatically to the Grid home as part of the Oracle Grid Infrastructure upgrade. If the database was using a nondefault listener, then Database Upgrade Assistant (DBUA) migrates the nondefault listener to the Oracle Database home.