You should update the data flow if you have changed the associated EPC.
Always perform this action after having changed objects that have a connection to the function. For example, if you have connected a different organizational unit or a different dialog with a function of the Human task type, you must update the data flow.
Procedure
The data flow is updated. All objects that were exchanged in the EPC are exchanged with their connections in the data flow, as well. Constants or properties are updated, too.