IPA FE Subject A sample Question 46
A question IPA Japan published in 基本情報技術者試験 科目A サンプル問題 問46, translated into English. ITPEC is based on the same exams.
Same question on ITPEC: Nov 2021 Q58
In the event of a disk failure, which of the following is a method for recovering a database by restoring a full backup data onto a disk from a tape, and then reflecting, from logs, post-update copies after the full backup was taken?
Explanation
Roll forward — restore the backup, then reapply the after-images from the log up to the failure.
After a disk (media) failure the data on the disk is lost, so recovery starts from the last full backup and then reapplies, from the log, the post-update images of the transactions committed since that backup. The database returns to its state just before the failure.
Answer (c)
Why not others:
- •(a) Checkpoint restart — resumes a program or system from a checkpoint taken during processing, when the stored data is still intact; it does not restore a backup from tape.
- •(b) Reboot — restarts the system and recovers no lost data.
- •(d) Rollback — uses the before-images in the log to undo uncommitted transactions after a transaction or system failure, moving the database backward, not forward from a backup.
Key rule: A media failure needs the backup plus roll forward with after-images; a transaction or system failure with the disk intact needs rollback of uncommitted work with before-images.
Databases · AI-written, may contain errors
This question comes from the past questions IPA Japan publishes, translated into English by ITPEC Practice. ITPEC Practice is an independent study tool and is not affiliated with IPA or ITPEC. See the original paper (PDF) or Report an issue.