Transaction Log Backup and Restore
A transaction log backup makes a copy of only the log file. A log file backup by itself cannot be used to restore a database. A log file is used after a database restore to recover the database to the point of the original failure. For example, a site performs a database backup on Sunday night and a log backup on each of the other nights. If one of the data disks for the database is lost at 2:30 P.M. Tuesday, the site can:
- Back up the current transaction log.
- Restore the database backup from Sunday night.
- Restore the log backup from Monday night to roll the database forward.
- Restore the log backup taken after the failure. This will roll the database forward to the time of the failure.
A transaction log recovery requires an unbroken chain of transaction log backups from the time of the database backup to the time of the failure.