TNS_ADMIN value set in Oracle for point one tnsnames.ora file

Use of TNS_ADMIN is defined for tnsnames.ora location when multiple installation of Oracle homes and client are done. TNS_ADMIN environment variable is specify the directory location for the tnsnames.ora file.

If tnsnames.ora is not properly set then it will give the following errors:
ORA-12154: TNS: could not resolve service name or SQL*NET Unable to resolve service name

Set in Environment Variable of Windows:

1. Search the Environment Variables and open window.
2. In the System variables section click the New button for create new entry.
3. Enter a variable name as TNS_ADMIN then enter a variable value of the path to the TNSNAMES.ORA file that will be used as the default.
   For example:
   Name: TNS_ADMIN
   Value: C:\Oracle\dbhomeXE\network\admin

For set at command prompt:

SET TNS_ADMIN=C:\Oracle\dbhomeXE\network\admin