version-compatible database files Definition
Files generated by the 
                     Quartus® Prime software that are a
                  version-compatible representation of the internal database files.
                  You can create version-compatible database files by using
                  quartus_cdb with the --export_database option,
                  the Tcl command export_database, or the Export
                     Database command (Project menu). You can also recreate internal
                  database files from version-compatible database files by using
                  quartus_cdb with the --import_database option,
                  the Tcl command import_database, or the Import
                     Database command (Project menu). The following are
                  version-compatible database file types:
               
- Atom Netlist File (.atm)
 - Hierarchy Database Export File (.hdbx)
 - Routing Constraints File (.rcf)
 - XML Report Database File (.xml)
 
There is also a Database Information File (.db_info) that dates the database files.