AutoCAD^® drawings consist largely of structured containers for database objects. Database objects each have the following features:

• A handle whose value is unique to the drawing/DXF file, and is constant for the lifetime of the drawing. This format has existed since AutoCAD Release 10, and as of AutoCAD Release 13, handles are always enabled.
• An optional xdata table, as entities have had since AutoCAD Release 11.
• An optional persistent reactor table.
• An optional ownership pointer to an extension dictionary which, in turn, owns subobjects placed in it by an application.

Symbol tables and symbol table records are database objects and, thus, have a handle. They can also have xdata and persistent reactors in their DXF records.