A user-defined mapping output is a numeric value or date that a mapping returns by aggregating a field or expression from each row in the mapping. For example, you might need to know when orders reach a specific threshold. You can configure the mapping to return the total order amount that the mapping processed. Define a mapping output called TotalOrderAmt and configure the mapping to summarize the Order_Amount field from every row. Define an expression or port name to aggregate in an Expression transformation.

A system-defined mapping output is a built-in value that the mapping always returns whenever the mapping completes. The mapping returns the number of source rows, the number of target rows, and the number of error rows that the mapping processes. You might pass these values in workflow variables to another task in a workflow, such as a Notification task or an Exclusive Gateway task. You do not have to define a system-defined mapping output.