Home  >  Oracle Database Administration (DBA)  >  Architecture  >  Oracle Database Listener (Q & A) 

1.  What happens to connected users when the listener goes down ?

Connected users will still be connected to the database. Users trying to establish new connections to the database (after stopping the listener) will not be able to connect until the listener is restarted.

2.  What is an Oracle Database Listener ?

An Oracle Database Listener is an Oracle Database Process which "listen" for for users (clients) connecting to the database. The listener process, either creates a dedicated server process for each user or to a shared multithreaded process that handles many users.

3.  Is it necessary to have a listener running in order to connect to the database ?

No. If the listener is NOT running, we can connect to the database if we are connected directly to the server.  

4.  How could I configure the Listener ?

The listener could be configured in listener.ora. Here is an example of  $ORACLE_HOME/nwtwork/admin/listener.ora:

Here 2 listeners are configured for this server. 

We can have also one listener which listen to 2 ports.  Here is an example:

5.  If I configured many listeners on my server, how could I see which is used ?

Using LSNRCTL> show current listener command. 

6.  How could I see if the listener is running ?

The status of the listener shows if the listener is running. If the listener process is running we can see more details about the process: 

More information about  this subject ( Oracle Database Listener ) you can get from  www.in-oracle.com

Definition of:  Oracle listener

A part of the Oracle DBMS that "listens" for users connecting to the database. It directs the queries to a function that either creates a dedicated server process for each user or to a shared multithreaded function that handles many users. The latter method may be chosen by the administrator to conserve memory. This definition was taken from here.