Configuring a network listener for Oracle on CentOS 6.2

You require to configure and run a network listener before creating a database with the Oracle's Database Configuration Assistant (dbca) tool. This is a how to configure such a listener.

I assume you already install a Oracle 11g Database Server on CentOS 6.2 with SSH X11 Forwarding and you are using a Linux client with a Desktop Environment like Gnome or KDE.

1. Login on the server using oracle user with SSH X11 Forwarding:

$ ssh -Y oracle@SERVER

2. You already had the $ORACLE_HOME/bin on the PATH environment variable (see ~/.bash_profile here) so you can issue:

$ netca

3. Choose Listener Configuration on the Welcome panel:

4. Select Add as the action:

5. Type a listener name, I recommend the default  "LISTENER":

6. Select protocols among the available, I choose TCP only:

7. Choose a listening port, I recommend the default "1521" but you can change it if you want. NOTE: Remember to open this port on iptables if you want remote database access, otherwise you won't be able to use it:

8. On More Listeners panels, choose No.

9. If you finish gracefully the wizard, you should be able to see this on the standard output. Observe that the listener is running.

$ netca 

Oracle Net Services Configuration:
Configuring Listener:LISTENER
Listener configuration complete.
Oracle Net Listener Startup:
    Running Listener Control: 
      /opt/app/oracle/product/11.2.0/db_1/bin/lsnrctl start LISTENER
    Listener Control complete.
    Listener started successfully.
Oracle Net Services configuration successful. The exit code is 0

you can manually stop the listener by issuing:

$ lsnrctl stop LISTENER

  then start the listener by:

$ lsnrctl start LISTENER

and check the listener status:

$ lsnrctl status LISTENER
LSNRCTL for Linux: Version 11.2.0.1.0 - Production on 06-FEB-2012 16:53:04

Copyright (c) 1991, 2009, Oracle.  All rights reserved.

Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=myserver)(PORT=1521)))
STATUS of the LISTENER
------------------------
Alias                     LISTENER
Version                   TNSLSNR for Linux: Version 11.2.0.1.0 - Production
Start Date                06-FEB-2012 16:49:47
Uptime                    0 days 0 hr. 3 min. 17 sec
Trace Level               off
Security                  ON: Local OS Authentication
SNMP                      OFF
Listener Parameter File   /opt/app/oracle/product/11.2.0/db_1/network/admin/listener.ora
Listener Log File         /opt/app/oracle/diag/tnslsnr/soabpm/listener/alert/log.xml
Listening Endpoints Summary...
  (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=soabpm)(PORT=1521)))
The listener supports no services
The command completed successfully

or verify if the listener is alive and locally reachable via TNS ping:

$ tnsping localhost 1521

TNS Ping Utility for Linux: Version 11.2.0.1.0 - Production on 06-FEB-2012 16:55:34

Copyright (c) 1997, 2009, Oracle.  All rights reserved.

Used parameter files:

Used HOSTNAME adapter to resolve the alias
Attempting to contact (DESCRIPTION=(CONNECT_DATA=(SERVICE_NAME=))(ADDRESS=(PROTOCOL=TCP)(HOST=127.0.0.1)(PORT=1521)))
OK (0 msec)

...
OK (0 msec)

to ensure the same thing remotely you must issue. NOTE: Remember to configure iptables to allow remote access.  

$ tnsping myserver 1521

NOTE: Remember you must a have a running listener before creating a database.
10. One final step is to add the ORACLE_HOME_LISTNER environment variable to oracle's ~/.bash_profile. Login to the server as oracle user and edit:

$ nano ~/.bash_profile

then append:

export ORACLE_HOME_LISTNER=LISTENER

at the end the ~/.bash_profile archive should look like:

# .bash_profile

# Get the aliases and functions
if [ -f ~/.bashrc ]; then
 . ~/.bashrc
fi

# User specific environment and startup programs
PATH=$PATH:$HOME/bin

umask 022

export TMPDIR=$TMP
export ORACLE_BASE=/opt/app/oracle
export ORACLE_HOME=$ORACLE_BASE/product/11.2.0/db_1
export LD_LIBRARY_PATH=$ORACLE_HOME/lib:/lib:/usr/lib
export PATH=$ORACLE_HOME/bin:$PATH

# The SID for a database, See http://eduardo-lago.blogspot.com/2012/02/creating-new-oracle-11g-r2-database-on.html 
export ORACLE_SID=demo 
export ORACLE_HOME_LISTNER=LISTENER