The Oracle Net Listener (or simply the listener) is the gateway to
the Oracle instance for all nonlocal user connections. A single listener can
service multiple database instances and thousands of client connections.
Enterprise Manager is one of the ways to access the listener. You
can control the configuration of the actual listener as well as general
parameters such as password protection and log file locations.
Advanced administrators can also configure Oracle Net Services by
manually editing the configuration files, if necessary, with a standard operating
system (OS) text editor such as vi or gedit or notepad
