ORA-12541 🗃️ SQL

ORA-12541: TNS:no listener

Nothing listens on the Oracle host/port — the listener is down or you have the wrong port.

Seen on: SQL

Meaning

The Oracle listener (lsnrctl) must be running on the port in your connect string (default 1521).

Common causes

  • Listener stopped
  • Wrong host/port
  • Firewall

⚡ Quick fix

  1. lsnrctl status / lsnrctl start on the server
  2. Verify host and port
  3. Open 1521 in firewalls

Detailed fix by platform

Linux

  1. lsnrctl status

How to diagnose

  1. Listener — Running on that port?
  2. Recent change — Did it start after a deploy, upgrade, or configuration change? Compare with the last working version.

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