Self-describing trail files are the default trail file format. Oracle recommends that you use self-describing trail files. You should only use SOURCEDEFS OVERRIDE and TARGETDEFS OVERRIDE for backward compatibility with trail file formats lower than 12.2.

If using the self-describing trails, then the column names on the source are mapped to the column names in the target table. Order of columns doesn't matter and if column names are different, then they need to be explicitly mapped using COLMAP.