Oracle Database / Connections & Oracle Net
ORA-12541: locate the listener endpoint before restarting services
A no-listener response points to the connection endpoint rather than the user's SQL privileges. Confirm the exact host, protocol and port first.
Environment and inputs: Oracle Database 19c baseline · SQL*Plus-compatible SQL unless RMAN, DGMGRL, ADRCI or a host shell is specified. Check release, patch level, edition and container first.
Start with this diagnostic
Use the stated SQL, RMAN, DGMGRL or host shell and replace sample names with approved targets. DBA and V$ views need authorized catalog access in the correct container. Do not grant broad privileges for an example.
lsnrctl status LISTENERRead the result
On the authorized database host, the status lists listener endpoints if this listener is reachable locally. It does not show whether an external firewall permits the client path.
Resolve and verify
Compare the application descriptor with the endpoint and inspect listener service management. Start or repair only the intended managed listener after checking the cluster or operating-system owner.
Operational precautions
Do not restart every listener or change public firewall access. The database may be healthy behind a different port or SCAN endpoint.