What is a 4DL file? A 4DL log file is utilized to record modifications made to a 4D database (.4DD) file. This file is stored alongside the database file and shares a similar filename. Its purpose is to accurately track and maintain a comprehensive record of the updates implemented within the database. A 4DD file, as compared to the 4DL file, is mainly associated with the 4th Dimensions by the 4D Inc.