ITPEC FE Morning April 2018 Question 30
ITPEC FE Morning April 2018 — Question 30 of 80
Two-Phase Commitment (2PC) — protocol for committing transactions across distributed database sites.
In a distributed database, when a transaction spans multiple sites, two-phase commit ensures all-or-nothing finalization:
- •Phase 1 (Prepare): coordinator asks all sites whether they can commit
- •Phase 2 (Commit/Abort): if all sites agree → commit everywhere; if any site refuses → abort everywhere
Why not others:
- (a) Exclusive control — locking mechanism for concurrency, not transaction finalization
- (b) Roll back — undoing a failed transaction, not a finalization method
- (c) Roll forward — redo recovery using logs after a crash, not finalization
Key rule: "inquiry to multiple sites whether finalization is possible" = Phase 1 of 2PC.
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