The compiler creates an XFD for each indexed file in the compiled program when you specify the "-Fx" compile-time option. XFDs are fully portable, and thus no recompilation is necessary if you change hardware. The compiler option "-Fxa" causes the generation of XFDs for indexed, relative and sequential files for use with International character translation only. The compiler option "-Fx3" generates version 3 XFD files for backwards compatibility with older versions of the runtime (indexed files only).
See Chapter 5 in Book 1, "User's Guide" of the ACUCOBOL-GT compiler documentation for details on how the XFD files are generated from the COBOL program's FDs.
Creating XFD files at compile time offers two significant advantages:
Any changes made to the file definitions are automatically included in the data dictionaries when the program is recompiled.
The effects of all compile-time options, COPY REPLACING, source-code control
lines, and Data layout compiler flags (-D...) are reflected correctly in the
XFDs.
More:
3.2.1 Understanding How the Database Table is Formed
3.2.2 Defaults Used in XFD Files