Critical severityconnectivity
Oracle Database Error:
ORA-12541
What does this error mean?
The TNS client could not connect to Oracle because no listener is running on the target host and port.
Common causes
- 1Oracle listener service is stopped on the target server
- 2Wrong port number in the connection string (default is 1521)
- 3Firewall blocks port 1521 between the pipeline server and Oracle host
- 4Oracle was restarted but the listener was not started
- 5Oracle runs on a non-default port that is not specified in the connection string
How to fix it
- 1Step 1: Check if the listener is running on the Oracle host: `lsnrctl status`.
- 2Step 2: Start the listener if stopped: `lsnrctl start`.
- 3Step 3: Test network connectivity: `telnet <oracle_host> 1521`.
- 4Step 4: Verify firewall/security group rules allow TCP on port 1521 from the pipeline server.
- 5Step 5: Confirm the port in the connection string matches the listener port in listener.ora.
Example log output
ORA-12541: TNS:no listener
ADF: UserErrorCannotConnectToOracle - No listener at host oracle-prod.company.com:1521