What is a reserved CAD field?
ArcGIS utilizes specific field schema for reading and writing CAD data. A reserved CAD field is an attribute field that exposes a property in a CAD file for geometry, layers, text, or user-defined attributes. Field names are standardized across AutoCAD and MicroStation formats and may not match the property names exactly as they are defined by the source CAD platform.
Read-only CAD fields
Read-only CAD fields are used in the CAD feature class virtual tables. When you add CAD data to ArcMap, CAD property fields that are nonessential for rendering or query operations are turned off by default. You can turn them on using the Fields tab on the Layer Properties dialog box.
Reserved CAD fields
Reserved CAD fields are used by the Export To CAD tool to override the tool's default behavior and generate specific CAD output. You can use them to create CAD data that conforms to specific standards.
The Export To CAD tool reads any valid reserved field value for each feature record and generates the specified output in the destination CAD file. Similarly, reserved CAD fields can also be used to separate input features and export them to individual CAD files.
You can add reserved CAD fields directly to a geodatabase feature attribute table or manage them separately in stand-alone tables and join them to existing tables. You can create them individually or add them in predefined groups using the Add CAD Fields tool.