Is it a Virus?
NO - Safe
Must be in C:\oracle\product\19.0.0\dbhome_1\BIN\tnslsnr.exe
Warning
Multiple listener instances
Sometimes several listeners run for different DB services; check services.msc to confirm.
Can I Disable?
YES
Stop the Oracle TNS Listener service in Services.msc or disable the startup option in Windows services.
What is tnslsnr.exe?
tnslsnr.exe is the Oracle Net Listener process that runs on Oracle database servers to accept client connection requests. It acts as the network entry point, directing requests to the appropriate database service, performing initial handshakes, and coordinating session establishment between clients and database instances.
tnslsnr.exe runs as the Oracle Net Listener service. It reads listener.ora and tnsnames.ora to resolve service names, listens on port 1521 by default, and routes connections to the correct database instance via dedicated or multiplexed servers.
Quick Fact: The Oracle Net Listener is essential for client applications to reach Oracle databases; it acts as a centralized entry point.
Types of Listener Processes
- Listener Process: Main network listener handling inbound connections
- Service Handler: Routes requests to appropriate database services
- Cache and Protocol Handlers: Manages connection requests, negotiation, and session setup
Is tnslsnr.exe Safe?
Yes, tnslsnr.exe is safe when it's the legitimate file from Oracle and running as the Oracle Net Listener service.
Is tnslsnr.exe a Virus or Malware?
The real tnslsnr.exe is NOT a virus. However, malware may masquerade as it; verify signature and location.
How to Tell if tnslsnr.exe is Legitimate or Malware
- File Location: Must be in C:\oracle\product\\dbhome_1\BIN\tnslsnr.exe or an Oracle Home BIN directory. Any tnslsnr.exe outside Oracle directories is suspicious.
- Digital Signature: Right-click tnslsnr.exe in File Explorer → Properties → Digital Signatures. Should show "Oracle Corporation".
- Resource Usage: Normal operation shows low CPU and modest memory. Constant high usage or spikes during idle times is suspicious.
- Behavior: Listener should start with Oracle services and only run when Oracle is active. Unexpected background behavior warrants malware scan.
Red Flags: If tnslsnr.exe is located outside Oracle directories (like Temp or User folders), lacks a valid signature, or remains active when the database services are stopped, scan your system.
Why Is tnslsnr.exe Running on My Server?
tnslsnr.exe runs to accept and route client connection requests to Oracle database instances. It starts with the database and remains active to listen for new connections.
Reasons it's running:
- Active Client Connections: Clients connect to the listener to establish sessions with Oracle databases
- Database Startup and Availability: Listener starts as part of the database startup sequence and remains running while the DB is available
- Multiple Services: If multiple Oracle DB services are configured, separate listeners may be used per service
- Network Resolution: Performs service name resolution using listener.ora and tnsnames.ora to map network endpoints
- Load Balancing and Failover: Configured for load balancing or failover across database instances and services
Can I Disable or Remove tnslsnr.exe?
Yes, you can disable the Oracle Net Listener. Stopping the listener stops new connections; ensure databases are not affected.
How to Stop tnslsnr.exe
- Stop Listener Service: Open Services.msc and stop the Oracle TNS Listener service
- Disable Startup: Set the Oracle TNS Listener service to Disabled in Services.msc
- Graceful Shutdown: From the Listener control utility (lsnrctl), issue STOP or SHUTDOWN commands if available
- Prevent Auto-Start: Remove the listener startup script from Oracle environment or disable the Windows Service
- Alternative Quick Stop: If you cannot stop the service, stop the database or disconnect clients to reduce load
How to Uninstall Oracle Net Listener
- ✔ Uninstall Oracle Grid or Database client components that include the listener
- ✔ Use Oracle Universal Installer (OUI) to remove Oracle Client or Database components that include tnslsnr.exe
- ✔ Consult Oracle documentation for your exact version and environment
Common Problems: Listener Issues
If tnslsnr.exe is not behaving, check common issues.
Common Causes & Solutions
- Listener not starting: Verify Oracle services are installed; ensure the listener is defined in listener.ora and configured in listener.ora; start service via lsnrctl or Services.msc.
- Port conflict: Check port 1521 or configured port; use netstat -ano | findstr 1521 to identify; change listener port or stop conflicting service
- Firewall blocking: Allow inbound connections to port 1521 in Windows Firewall or network firewall
- Invalid service name: Check tnsnames.ora entries; ensure service names match listener configuration; reload listener with lsnrctl reload
- Corrupt listener configuration: Review listener.ora; revert to backup or regenerate from install; restart listener
- Outdated Oracle components: Update to the latest patchset; reinstall if necessary; ensure compatibility with database version
Quick Fixes:
1. Check listener status with lsnrctl status
2. Verify port with netstat and firewall rules
3. Restart listener with lsnrctl stop && lsnrctl start
4. Review listener.ora for correct host and port
5. Check database alert logs for listener errors
Frequently Asked Questions
Is tnslsnr.exe a virus?
No, the legitimate tnslsnr.exe from Oracle is not a virus. Ensure it is located under C:\oracle\product\<version>\dbhome_1\BIN\tnslsnr.exe and has a valid Oracle digital signature.
Where is tnslsnr.exe located?
Typically under C:\oracle\product\<version>\dbhome_1\BIN\tnslsnr.exe, depending on your Oracle Home directory.
What port does tnslsnr.exe listen on?
Default port is 1521 unless configured otherwise in listener.ora.
How do I restart the Oracle TNS Listener?
Use lsnrctl stop followed by lsnrctl start, or restart the Oracle service using Windows Services.msc.
Can I disable the listener without affecting the database?
Disabling the listener will prevent new connections; existing sessions may continue until they timeout or are closed, but best practice is to gracefully shut down applications first.
Why are there multiple tnslsnr.exe processes?
In some configurations, multiple listener services or instances may be running for different Oracle Homes or databases; ensure they are legitimate by checking listener.ora and services.msc.