Oracle 19c Installation guide (Linux/ Windows)

How to configure Oracle Listener Step-by-Step Guide

 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

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 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.

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