Oracle Listener
- A server-side
process that listens for incoming client connection requests to Oracle
databases.
- Uses
the listener.ora configuration file, typically located in:
- $ORACLE_HOME/network/admin
(Linux)
- %ORACLE_HOME%\network\admin
(Windows)
Step-by-step Listener Configuration
Create/Modify listener.ora
Configure tnsnames.ora
Start the listener (lsnrctl start)
Test connectivity using tnsping
Register services if needed (ALTER SYSTEM REGISTER)
Step1:Check if a listener is already running
lsnrctl status
- If it
says TNS-12541: TNS:no listener, no listener is running.
- Otherwise, it will display current listener status.
Step2️: Create/Modify listener.ora
cd $ORACLE_HOME/network/admin
Open listener.ora in your editor:
vi listener.ora
Add or modify:
LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS =
(PROTOCOL = TCP)(HOST = your-hostname-or-ip)(PORT = 1521))
(ADDRESS =
(PROTOCOL = IPC)(KEY = EXTPROC1521))
)
)
Explanation:
- PROTOCOL
= TCP: Network protocol.
- HOST:
Your server hostname or IP (localhost if local).
- PORT =
1521: Default Oracle listener port.
- PROTOCOL
= IPC: For local (inter-process) connections, including external
procedures.
Step3️:Create/Modify tnsnames.ora
(Client/Server)
In the same folder, edit tnsnames.ora:
ORCL =
(DESCRIPTION =
(ADDRESS =
(PROTOCOL = TCP)(HOST = your-hostname-or-ip)(PORT = 1521))
(CONNECT_DATA =
(SERVER =
DEDICATED)
(SERVICE_NAME =
orcl)
)
)
- ORCL is
your connection alias.
- SERVICE_NAME
should match your database service name (select value from v$parameter
where name='service_names';).
Step4️: Start the Listener
lsnrctl start
Verify:
lsnrctl status
You should see your listener, hostname, and port.
Step5: Test Listener Connection
tnsping ORCL
Expected output:
scss ok (20 msec)
This confirms your listener is reachable.
Step6: Add Database to Listener (if not automatically registered)
In SQL*Plus as SYSDBA:
ALTER SYSTEM REGISTER;
This will dynamically register your database with the
listener (Dynamic Service Registration).
Verify using:
lsnrctl services
You should see your database service listed under the
listener.
Step7: Stopping the Listener
To stop:
lsnrctl stop
To restart:
lsnrctl reload
Troubleshooting Tips
✅ Ensure port 1521 is open in
your firewall.
✅
Check listener.log in $ORACLE_HOME/network/log.
✅
If TNS: no listener, ensure the listener is running.
✅
Ensure your SERVICE_NAME in tnsnames.ora matches the database service name.
✅
Use ALTER SYSTEM REGISTER if the service does not appear after starting.
