ITPEC FE Morning October 2023 Question 58
Which of the following is a method that restores the system to its initial state and restarts it when a system failure occurs, that does not accompany preprocessing of a copy before/after an update, and that is also called initial program load?
Explanation
Cold start — the system is brought back to its initial state and restarted from scratch (initial program load), without applying before-images or after-images from the log.
Restart and recovery methods after a failure:
- •Cold start: the system is initialised and restarted, as with an IPL; no log processing, work in progress is lost
- •Warm start: the system restarts from the state just before the failure, using the log and checkpoints to keep processing
- •Rollback: undoes uncommitted transactions using before-images
- •Rollforward: reapplies committed updates to a backup using after-images
The question's clues, "initial state", "no copy before/after an update" and "initial program load", all point to a cold start.
Answer (a)
Why not others:
- •(b) Rollback — needs before-images (copies taken before an update) to undo changes
- •(c) Rollforward — needs after-images (copies taken after an update) and a backup to redo changes
- •(d) Warm start — resumes from the state at the failure, using the log, rather than from the initial state
Key rule: Rollback uses before-images, rollforward uses after-images, warm start resumes using the log; a cold start uses none of them and starts over.
Databases · AI-written, may contain errors
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