Before you can run a transformation, you must create a transformation configuration. When you apply a transformation configuration, an instance of the transformation is created and the transformation runs with the properties that the configuration defines.
If you select source elements in the model instead of using the transformation configuration, the source elements that you select override the source model or elements specified in the transformation configuration. The transformation configuration is not affected and the source that you specify on the Source and Target page of the Transformation Configuration editor or wizard does not change.