Databases created with a 6.7.x or 6.8.x version of 4th Dimension or 4D Server are completely compatible with 4D 2003 applications (structure files and data files).

However, the structure file will be converted on startup of the database with 4D 2003 and you will no longer be able to open it with prior versions of 4D. With 4D 2003, when you open a database created with a previous
version of 4D, a dialog box informs you that the structure file will be converted.

On the other hand, the data file is not converted and can be opened using a version 6.8.x of 4th Dimension or 4D Server.