SAP Message R8427 - The extractor can not fill field &2 of the extract structure &1

Diagnosis
The view specified for extraction cannot fill field &v2&. A field inthe extract structure, that is not filled automatically, must be in anappend. This field must be filled in the customer exit. This isreserved for customers.

System Response
The DataSource cannot be saved like this.

Procedure
Remove the field from the extract structure, or use a different view asan extractor.