Handle-based Automation
Sometimes the key for the database file is either not present in the drawing or is actually the AutoCAD Handle (the unique identifier that all AutoCAD entities have that remains the same throughout the life of the drawing). For these drawings we do a variation on Automated Area Linkage where the Database Key is the AutoCAD Handle and that is what is passed to the JavaScript (or other) function.
The layer for the area outline (“Room Polygon”) is defined by the Room Layer (RL) parameter. In addition, the “HB” (Handle Based) parameter is used to denote Handle-based processing is being used. If the HB parameter is not used and the Text Layer (TL) parameter is not defined (which would cause Automated Area Linkage to be used instead) then nothing occurs.
please see Database Linkage Parameters for details on parameter controls.