Modify TNSNAMES.ORA file to connect to an Oracle Database I would like to modify TNSNAMES.ORA file to connect to an ORACLE Database and I noticed that on my PC there are 3 different files with name TNSNAMES.ORA files. Which of these three should I modify in order to make connection

D:\app\XXX\product\11.2.0\client_32\network\admin
E:\app\XXX\product\11.2.0\client_64\network\admin
D:\app\XXX\product\11.2.0\client_1\network\admin
You may start command prompt using windows commanline cmd and use below:

tnsping any_random_name




as you can see in the image, it uses parameter file where sqlnet.ora exists. This is the folder where your current oracle installation points to. You should make change in that folder's tnsnames.ora.