the RT2.dbf file is for reverse geocoding, but if you didn’t have it in the Geocoder index dataset and call the UsaGeocoder object it would throw exceptions, the reason is that in the UsaGeocoder object it has 9 internal plugins:
StreetMatchingPlugin, ZipDbfMatchingPlugin, CityDbfMatchingPlugin, StateDbfMatchingPlugin, CoordinatesMatchingPlugin, CountyDbfMatchingPlugin, CensusTractsDbfMatchingPlugin, CensusBlockDbfMatchingPlugin, CensusBlockGroupDbfMatchingPlugin.
When executing the geocoding function, it would through these 9 internal plugins one by one. So you must have the full index dataset when using usaGeocoder object.
Obviously you download the openstreetmap dbf file from our website and there is no rt2.dbf file, the rt2.dbf file was generated by us, it is not a dbf file that combined to the shp file. If you missed the rt2.dbf file please contact ThinkGeo support to get complete MapSuiteGeocoder index dataset.
Any more questions please let me know,