If you change the table definitions in the mapping VMD file, or you add a new message definition to the VMD file, you must update the source data tables in the database that you have specified for this channel. There are two ways to update these data tables:

• Re-export the Source Data Tables: This will drop the existing data tables and replace them with new ones. Any data in the existing tables is lost, which may lead to undesirable results. (See Exporting Tables for more details on re-exporting the source data tables.) Also, the status tables for every message definition in the VMD file will be dropped and recreated.

• Modify the existing databases manually: Any columns that you add to a table definition in the VMD file must be manually added to its corresponding database table. You must also create a new status table for each new message definition you have added to the VMD file; for more information on status tables, see Basic Database Schema.