ATX files exist as 2 different types. Please find information about each of them below.
Type 1: ArcGIS Attribute Index File
ATX files store ArcGIS attribute indexes for shapefiles or dBASE files. ArcGIS is a mapping and analysis tool by ESRI. ATX indexes are created in ArcCatalog. ArcView 3.x indexes are not used in ArcMap...
ATX files store ArcGIS attribute indexes for shapefiles or dBASE files. ArcGIS is a mapping and analysis tool by ESRI. ATX indexes are created in ArcCatalog. ArcView 3.x indexes are not used in ArcMap or ArcCatalog. But ArcObjects can convert ArcView indexes to ArcGIS 8 indexes. No public specifications exist for the ATX format.
The .atx extension relates to an Animation:Master plugin for Windows and macOS. These files contain data exclusive to the software. Proprietary file formats protect developer intellectual property.
ATX files store ArcGIS 8 attribute indexes. An .atx file is created for each shapefile or dBase index in ArcCatalog. ArcView GIS 3.x indexes are not used by ArcMap or ArcCatalog. A new attribute model indexes shapefiles and dBASE files. ArcObjects Help offers a tool converting ArcView indexes to ArcGIS 8 indexes.
Shapefiles store geographic feature locations and attributes. Required shapefile extensions are: .shp storing feature geometry, .shx storing geometry indexes, .dbf storing attribute data. Geometry and attributes share a one-to-one record number relationship.
ArcGIS Desktop
Animation Master