Recovery Techniques in database management system free notes pdf
1. If database has been damaged:
Need to restore last backup copy of database and reapply updates of committed transactions using log file.
2. If database is only inconsistent:
- Need to undo changes that caused inconsistency. May also need to redo some transactions to ensure updates reach secondary storage.
- Do not need backup, but can restore database using before- and after-images in the log file.