PROBLEM:

While starting the listener, getting an error like TNS-12542: TNS:address already in use

SOLUTION:

To find out the issue, Let’s check the content of the listener in listener.ora file.

Inside the listener entry, we have 2 ADDRESS entries with same host and same port number(1524) . So starting the listener is failing with conflict.

To fix the issue, give different ports for both the ADDRESS entries.

the listener will look as below:( 1524 and 1525)

Now start the listener.

Listener started successfully and listening on both 1524 and 1525 port. So in simple words, port should be unique for each ADDRESS entry of the listener.