Listener waiting requests from Clients to connect to the Instance. By default, the Listener name is (amazingly enough)“Listener” (but you can call it anything you like). It listens for connection requests on aparticular port (the default port number in 8.0 and above is 1521, but once again you canset this to any valid port number if you wish). A client knows where to contact the Listener (the machine it’s running on, and the port it’s listening on) because a local configuration file, called “tnsnames.ora”, gives it the necessary information. More advanced configurations can dispense with the tnsnames.ora .
How to Register Listener In Database
1.) Static Instance Registration
2.) Dynamic Instance Registration
Lets Discuss These Method and Start With Static Instance Registration :
Its basic method , and use $ORACLE_HOME\NETWORK\ADMIN\listener.ora its look like
LISTENER =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = xx.xx.xx.xx)(PORT = 1521))
)
And When You Fire lsnrctl status , instance Name Appear with Unknown like the following :
Service “orcl” has 1 instance(s).
Instance “orcl”, status UNKNOWN, has 1 handler(s) for this service…
Service “orcl” has 1 instance(s).
Instance “orcl”, status UNKNOWN, has 1 handler(s) for this service…
The command completed successfully
The status is unknown because there is no mechanism to guarantee that the specified status even exists.Here the listener assumes that instance will be there whenever there will be any request. It donot have inforamtion about the status of the Current Instance.
Dynamic Instance Registration (service registration):
in this Way the PMON is Responsible about Register Listener ,
Benefit for this way like the following :
Services Summary…
Service “ORCL” has 1 instance(s).
Instance “ORCL”, status READY, has 1 handler(s) for this service…
Service “ORCLXDB” has 1 instance(s).
Instance “ORCL”, status READY, has 1 handler(s) for this service…
Service “ORCL2” has 1 instance(s).
Instance “ORCL2”, status READY, has 1 handler(s) for this service…
The command completed successfully
To register Database name with listener in this way you could use :
SQL> ALTER SYSTEM REGISTER;
Thank you
Osama Mustafa
Technology Geek 