extension table

In the AVEVA Historian, an extension table is a table that provide a means for handling acquired plant data. Extension tables are not part of normal SQL Server functionality. A normal SQL Server table stores data directly to the database file. An extension table, however, is a logical table that is populated from the data files created by the historian storage system. Data in the extension tables can be manipulated by using normal Transact-SQL code, as well as the specialized time domain extensions provided by the historian. See also view, configuration table.