A differential backup only backs up record data that has changed since the last differential backup was initialized. For example, if you have a large database or large tables that cause a slow backup, you could instead initialize a differential backup, and then call all subsequent backups sending the differential option. These subsequent backups would only process tables and records that had been modified since the last backup was performed. This can significantly improve backup performance.
A differential backup should be reinitialized whenever changes, such as table structure modifications or index deletions and additions, are made. To reinitialize the differential backup, run the backup command with the ‘PrepareDiff’ option.
Differential backups are only supported on Advantage proprietary tables (ADT tables).