Q8 (1/1) Choose the correct description of database replication processing.

Database replication for physical failure recovery uses write-ahead logging (WAL), where journal entries are written before applying updates to the database. This ensures that if a physical failure occurs during an update, the transaction can be recovered from the journal. Logical failures (data corruption, wrong values) occur after updates and cannot be prevented by pre-update journaling alone.

Step-by-step Derivation:
Key concepts: (1) Journal file timing: 'before' = write-ahead logging (WAL), prevents data loss on crash; 'after' = too late to prevent failure. (2) Failure types: Physical failure = hardware crash, power loss, disk failure (prevented by WAL); Logical failure = incorrect data written, application error (requires rollback/undo). (3) Replication for physical failures uses the before-update pattern: write to journal → write to main database → acknowledge. If crash occurs between steps, journal can recover. Therefore, option A is correct.