Virtual Labs

What is the main goal of the Two-Phase Commit (2PC) protocol?

a: Maximize throughput by parallelizing commits Explanation

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b: Ensure durability of local transactions only Explanation

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c: Guarantee atomic commit or abort across all participants Explanation

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d: Provide non-blocking consensus in all failure cases Explanation

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Which two phases make up the Two-Phase Commit protocol?

a: Prepare and Commit/Abort Explanation

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b: Lock and Unlock Explanation

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c: Begin and End Explanation

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d: Vote and Ack Explanation

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What durable log entry does a participant write before replying VOTE_COMMIT?

a: INIT Explanation

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b: READY Explanation

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c: COMMIT Explanation

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d: ABORT Explanation

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If a participant crashes after logging READY but before receiving GLOBAL_DECISION, what must it do on recovery?

a: Unilaterally abort the transaction Explanation

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b: Unilaterally commit the transaction Explanation

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c: Query the coordinator for the global decision Explanation

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d: Start a new transaction Explanation

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What happens if the coordinator crashes after sending some but not all GLOBAL_COMMIT messages?

a: Only the nodes that received it commit, others abort Explanation

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b: Protocol deadlocks permanently Explanation

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c: On recovery, coordinator re-sends the decision to stragglers Explanation

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d: Participants that didn’t get it commit by default Explanation

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Which of the following is a known drawback of Two-Phase Commit?

a: It never aborts even on failures Explanation

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b: It can block if the coordinator fails mid-protocol Explanation

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c: It provides no atomicity guarantees Explanation

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d: It requires quadratic message complexity Explanation

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What optimization to 2PC reduces logging overhead by assuming abort if no commit record exists?

a: Presumed Commit Explanation

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b: Presumed Abort Explanation

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c: Three-Phase Commit Explanation

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d: Two-Phase Locking Explanation

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2 phase commit With different failures