Use the TableDataUpgradeExtension to specify the file extension used by the engine for backup copies of the physical data file that makes up part of a logical DBISAM table. Backup files that use this file extensions are created specifically when upgrading a table from a prior version format to the latest table format. The default value is ".dup". Be sure to always include the filename extension separator (.) when specifying the file extension.
This property cannot be set while the engine is active and the TDBISAMEngine Active property is True.