ITPEC FE Morning October 2020 Question 28
ITPEC FE Morning October 2020 — Question 28 of 80
Database Recovery — Rollforward — restore a database after storage failure using backup files and a log.
When a storage unit fails (media failure), the database must be recovered from the last backup combined with the transaction log:
- •Rollforward (redo) — restores backup, then replays committed transactions from the log to bring the DB up to the point of failure
- •Rollback (undo) — reverses uncommitted transactions; used after a system crash, not media failure
Why not others:
- (a) Archive — creating a backup copy, not a recovery operation
- (b) Checkpoint dump — flushing in-memory data to disk at a point in time; part of recovery infrastructure but not the recovery process itself
- (c) Commit — finalizing a transaction; unrelated to disaster recovery
Key rule: Media failure → backup + log → rollforward. System crash (no data loss) → log → rollback uncommitted transactions.
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