How to Fix ORA-12560: TNS Protocol Adapter Error in Oracle

2 min read

If you’ve just installed Oracle Database and tried connecting using SQL*Plus, you might have seen this frustrating error:

Don’t worry — this is one of the most common Oracle errors on Windows, and it’s very easy to fix.

Let’s understand what it means and how to resolve it step-by-step.

What Causes ORA-12560?

The error means that Oracle can’t connect to a running database instance because the required background services (like the database or listener) are stopped.

On Windows, Oracle runs as background services, and if those aren’t active, SQL*Plus can’t connect — hence the “protocol adapter error.”

Step-by-Step Solution

Follow these simple steps to get your Oracle instance up and running again:

1. Open Windows Services

  • Click the Start menu.
  • Type services.msc and press Enter.

2. Find Oracle Services

  • In the Services window, press O to quickly jump to Oracle-related services.
  • Look for services like:
    • OracleServiceORCL (your main database service)
    • OracleOraDBHomeTNSListener (the listener service)
    • OracleMTSRecoveryService (optional)

💡 Note: “ORCL” may differ if you used a custom SID name during installation.

3. Start the Required Services

  • If any of these show a Stopped status:
    • Right-click → Start
  • Wait until their status changes to Running.

4. Reconnect Using SQL*Plus

Open Command Prompt again and run:

If everything is fine, you should now see:

Optional: Auto-Start Oracle Services

To avoid this issue after every reboot:

  • In the Services window, right-click each Oracle service → Properties
  • Set Startup type to Automatic

This ensures Oracle automatically starts whenever Windows boots up.

Still Not Working? Try These Checks

If you’re still getting the error, here are a few quick diagnostics:

1. Check Environment Variables

Make sure your system variables are correctly set:

  • ORACLE_HOME → path to your Oracle installation (e.g., C:\app\<user>\product\<version>\dbhome_1)
  • Add Oracle’s bin directory to your system PATH

2. Verify Listener Status

Run:

lsnrctl status

If the listener isn’t running, start it using:

lsnrctl start

3. Restart Your Computer

Sometimes a quick reboot ensures all Oracle services and background processes initialize properly.

Conclusion

The ORA-12560: TNS:protocol adapter error is a simple service-related issue — not a configuration or installation failure.
Starting the Oracle services via services.msc almost always fixes it instantly.

Whether you’re a DBA, developer, or student learning Oracle, remember this quick tip — it’ll save you time every time you see that red error line.