> But as far as I understand, the database has to track which page changes
> since which backup.

Correct, but that information is actually stored as a "version number" in the header of each data page. When page data changes the "version number" is changed.

The nbackup database structure only stores the "version number" for the backup level.

NBackup physically reads each page header to determine if the page "version" has changed since the last backup.

No list of the pages that have changed is stored within the database.


Sean