Oracle : TNSNAMES.ORA file

In Oracle, the tnsnames.ora file important configuration file that is used in Oracle database connection's

default location of tnsnames.ora file is $ORACLE_HOME/network/admin but it can be modified or kept at other locations as well and create soft links at the default location. while using a location other than the default location, we need to use the TNS_ADMIN parameter to load settings while starting the listener of the database.

In case you are not sure about the location of tnsnames.ora file, you can execute below commands on Unix shell

$env |grep ORACLE_HOME

or use below command 

echo $ORACLE_HOME

Syntax used in tnsnames.ora file

testdb.domain.com

(DESCRIPTION =

    (ADDRESS = (PROTOCOL = TCP)(HOST =  HOSTNAME.DOMAIN.COM) (PORT = 1521) 

)

(CONNECT_DATA =)

    ( SERVICE_NAME=tstdb.domain.com)

)

This file can be modified very easily, take backup before  modifying anything in this file

on Unix use vi editor to open the file and change anything we want then save using :wq

On Windows, one can use Notepad editor and save using ctrl+S or the save option