LISTENER.ORA is a configuration file used to control the operation of an Oracle listener on the server. You can have more than one listener configured in one LISTENER.ORA file if each has a unique name.
The listerner.ora file contains server side network configuration parameters. It can be found in the “$ORACLE_HOME/network/admin” directory on the server. The LISTENER describes an address list or set of address lists. Addresses consist of a protocol definition and a key value, or else a protocol definition, a hostname, and a port number. The generalized Oracle Database 11.2.0.4 standard fresh install LISTENER entry in the listener.ora file follows:
# LISTENER.ORA Network Configuration File: /u01/app/oracle/product/11.2.0.4/network/admin/listener.ora
# Generated by Oracle configuration tools.
LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = localhost.localdomain)(PORT = 1521))
)
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC))
)
)
)
SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(SID_NAME = PLSExtProc)
(ORACLE_HOME = /u01/app/oracle/product/11.2.0.4)
(PROGRAM = extproc)
)
(SID_DESC =
(GLOBAL_DBNAME = prod.com)
(ORACLE_HOME =/u01/app/oracle/product/11.2.0.4)
(SID_NAME = prod)
)
)
The SID_LIST_LISTENER, the second entry in the standard listener.ora file, contains the SID description. The Oracle Database 12c standard SID_DESC is defined by the SID_NAME, ORACLE_HOME, and PROGRAM parameter definitions. The SID_NAME parameter is defined as PLSExtProc, which is used as the extproc identifier. The ORACLE_HOME parameter defines the Oracle home directory. Finally, the PROGRAM parameter defines the extproc agent as the program.