If the source or target is a database, you can use connection variables.
To enter the database connection for the $Source and $Target connection variables:
In the session properties, select the Properties tab or the Mapping tab, Connections node.
Click the Open button in $Source Connection Value or $Target Connection Value field.
The Connection Browser dialog box appears.
Select a connection variable or session parameter.
You can enter the $Source or $Target connection variable, or the $DBConnection
Name
or $AppConnection
Name
session parameter. If you enter a session parameter, define the parameter in the parameter file. If you do not define a value for the session parameter, the Integration Service determines which database connection to use when it runs the session.