If you select to use Full – Back Up Files – Using modified time, Differential – Using modified time, or Incremental – Using modified time, Backup Exec uses a file’s modified time rather than the archive bit to determine if it needs to be backed up.
When Backup Exec runs a full or incremental backup, the time the backup launches is recorded in the Backup Exec database. The next time an incremental or differential backup launches, Backup Exec compares the file system time to the backup time recorded in the Backup Exec database. If the file system time is later than the database time, the file is backed up.
When an incremental backup is run, a new time is recorded in the Backup Exec database. The database time is not updated with differential backups.
Using the modified time allows Backup Exec to run differential backups on file systems, such as UNIX, which do not have an archive bit.
If you want Backup Exec to use modified time to determine if a file has been backed up, the full and incremental (or full and differential) backups must use the same backup selection list.
The Full – Using modified time backup method adds the time of the backup to the Backup Exec database only if the full backup job completes successfully. If the full backup job does not complete successfully, any subsequent backup jobs that use the differential or incremental modified time backup methods back up all of the data instead of just the data that changed since the last full backup.