If you choose the ODBC provider type, you can enable the Use DSN option to use the DSN configured in the Microsoft ODBC Administrator as the connect string. If you do not enable the Use DSN option, you must specify the server name and database name in the connection properties.

If you choose the OLEDB provider type, you must install the Microsoft SQL Server 2012 Native Client to configure native connectivity to the Microsoft SQL Server database. If you cannot connect to the database, verify that you correctly entered all of the connectivity information.

You can download the Microsoft SQL Server 2012 Native Client from the following Microsoft website: http://www.microsoft.com/en-in/download/details.aspx?id=29065.

After you upgrade, the Microsoft SQL Server connection is set to the OLEDB provider type by default. It is recommended that you upgrade all your Microsoft SQL Server connections to use the ODBC provider type. You can upgrade all your Microsoft SQL Server connections to the ODBC provider type by using the following commands:

If you are using PowerCenter, run the following command:
pmrep upgradeSqlServerConnection
If you are using the Informatica platform, run the following command:
infacmd.sh isp upgradeSQLSConnection

For specific connectivity instructions, see the database documentation.