Oracle Net Services Configuration on Windows

Oracle Net Service Subkeys
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services contains subkeys that correspond to services

OracleHOME_NAMEClientCache

OracleHOME_NAMECMAdmin

OracleHOME_NAMECMan

OracleHOME_NAMETNSListener


Listener Requirements
In Oracle Database 10g Release 1 (10.1), the listener is set to start automatically at system restart.

Single listener can SUPPORT MULTIPLE DATABASES.
or
If we want to use separate listener for each database then make sure listener configured to listen on different TCP/IP port numbers.

If some IP address or PORT are used then second or subsequent listeners would fails.

If we have more than one ORACLE_HOME with different Oracle Version then higher Oracle Version capable to listen lower version. we should configure higher version listener or stop lower version listener.

example : Oracle 10gr2 or Oracle 9ir2 on some machine.just configure oracle 10gr2 listener to listen both connection 10g or 9i. or stop oracle 9i listener services.


Understanding Optional Configuration Parameters

Oracle Net Service first checks for the parameters as environment variables, and uses the values defined. If environment variables are not defined, it searches for these parameters in the registry

LOCAL

You can use parameter LOCAL to connect to Oracle Database without specifying a connect identifier in the connect string.
connect identifier should be "NET SERVICE NAME"

Oracle Net checks if LOCAL is defined as an environment variable or as a parameter in the registry, and uses finance as the service name. If it exists, Oracle Net connects

TNS_ADMIN

You can add parameter TNS_ADMIN to change the directory path of Oracle Net Services configuration files from the default location of ORACLE_HOME\network\admin.

USE_SHARED_SOCKET

You can set parameter USE_SHARED_SOCKET to true to enable use of shared sockets. If this parameter is set to true, the network listener passes the socket descriptor for client connections to the database thread. As a result, the client does not need to establish a new connection to the database thread and database connection time improves. Also, all database connections share the port number used by the network listener, which can be useful if you are setting up third-party proxy servers.

This parameter only works in dedicated server mode in a TCP/IP environment