The database upgrade window will be displayed when the main database for the application requires and upgrade. This upgrade will make changes which are incompatible with earlier versions of the software making it unusable with those earlier versions. This is only an issue if a downgrade is required to an earlier version.
The database file will be backed up prior to performing the upgrade in case any problem occurs during the upgrade. This backup file can be used in case an older version needs to be re-installed.