Generating a difference (DIFF) file for catalog files. A second catalog file is compared with a first catalog file to identify at least a modified portion in the second catalog file. The modified portion indicates a difference between the content of the first catalog file and the second catalog file. A location of the modified portion is identified in the content of the second catalog file. A reference marker is assigned to the identified location with respect to the second catalog file. The DIFF file is generated indicating the modified portion and indicating the reference marker.