ORA-12541: TNS: no listener

Oracle Tips by John Garmany

You Asked:

I get the ORA-12541 error message when I try to connect through Forms6i and Reports6i Builder. I've started the listener also. I have no problems accessing the database through SQL*Plus. I've checked the listener.ora and tnsnames.ora files and everything seems okay.

We Said:

From the docs:

ORA-12541: TNS no listener

Cause: Listener for the source repository has not been started.

Action: Start the Listener on the machine where the source repository resides.

Basically the Forms server could not find the listener. First check the tnsnames.ora file and ensure that it points to the correct server and port. If the Forms server is on another machine, test the TNS resolve with tnsping from the command prompt. Finally, check the listener.

First, ensure that your listener service is running.

C:\Documents and Settings\ME>lsnrctl stat

This should show the status of the listener and the services it is listening for. Remember that when you run SQL*Plus on the database server, it does not need the listener to connect unless you specify the database tnsnames.ora entry.

Try to start the listener service using lsnrctl from DOS prompt.

set ORACLE_HOME= cd %ORACLE_HOME%/bin
lsnrctl start LISTENER

If the listener service is not running, re-start the listener service using the Windows task manager or use the DOS command line utility to re-start the Windows service with the "net start" command:

C:\Documents and Settings\ME>net start OracleOraDb10g_home1TNSListener

You can use the lsnrctl status command to verify that the listener is down, and lsnrctl start to start your listener. If you are on Windows, also verify that the listener service is running. Here are more notes on lsnrctl:

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