When multiple installation of Oracle homes and client are done, Use of TNS_ADMIN is defined for tnsnames.ora location. TNS_ADMIN environment variable  specifies 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: - Search the Environment Variables and open window. - In the System variables section click the New button for create new entry. - 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:\data\app\oracle\product\dbhomeXE\network\admin

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SET TNS_ADMIN=C:\data\app\oracle\product\dbhomeXE\network\admin

mkdir -p $ORACLE_BASE/network