Q8 /20 Choose the correct description of database rollforward processing.
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Choose the correct description of database rollforward processing.
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Answer: B. Restore using a journal file after updating against a physical failure.
Rollforward processing (also called roll-forward or redo) replays committed transactions from a journal/log file after recovering from a physical failure (disk corruption, system crash, etc.). This restores the database to its state before the failure by re-applying all logged updates. Rollback (not rollforward) handles logical failures by undoing transactions; rollforward is specifically the recovery mechanism for physical failures.
Step-by-step Derivation:
Rollforward vs. Rollback distinction:
- Physical failure (hardware/system crash): Use rollforward - restore backup, then replay journal to redo committed transactions
- Logical failure (bad SQL, incorrect updates): Use rollback - undo unwanted transactions
- Timing: Rollforward operates after the failure is detected and backup is restored, replaying logs forward in time
- Elimination: Options A and C mention logical failure or 'before' which are incorrect for rollforward
- Answer: B is correct - rollforward uses journal after physical failure to restore committed state