How to re-create the Oracle LISTENER if the listener fails to load, or no service instance(s) are assigned.

The listener is a separate process that runs on the database server computer. It receives incoming client connection requests and manages the traffic of these requests to the database server.

1. Launch Oracle Net Configuration Assistant (NCA)
   • Windows - Start > Programs > Oracle_11.x.x.x > Configuration and Migration Tools > Net Configuration Assistant
   • Linux - NCA needs to be started from a terminal window as the oracle user.
   1.     su - oracle
   2.     $ORACLE_HOME/bin/netca
2. Perform the following steps to delete the existing listener.
   1. Select Listener configuration, click Next.
   2. Select Delete, click Next.
   3. Select the listener to delete, click Next.
      • Default listener name is 'LISTENER'.
   4. Listener Deleted, click Next.
   5. Listener configuration, click Done.
3. Perform the following steps to create a listener.​
   1. Select Listener configuration, click Next.
   2. Select Add, click Next.
   3. Choose a listener name, click Next.
      • Default listener name is 'LISTENER'.
   4. For selected protocols, select TCP, click Next.
   5. Enter in the port used to connect to the oracle database, click Next.
      • Default port is 1521.
   6. Select No to configure another listener, click Next.
   7. Click Next to complete the listener configuration.
   8. Click Finish on the Welcome screen.