When you add an instance of an External Procedure transformation to a mapping, you can choose to connect it as part of the pipeline or leave it unconnected. Connected External Procedure transformations call the COM or Informatica procedure every time a row passes through the transformation.
To get return values from an unconnected External Procedure transformation, call it in an expression using the following syntax:
When a row passes through the transformation containing the expression, the Integration Service calls the procedure associated with the External Procedure transformation. The expression captures the return value of the procedure through the External Procedure transformation return port, which should have the Result (R) option checked.