Virtual Labs

2 Phase Commit with and without failures

During Phase 1 of two-phase commit, what message does the coordinator send to all participants?

a: COMMIT Explanation

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b: PREPARE Explanation

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c: VOTE_REQUEST Explanation

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d: BEGIN_TRANSACTION Explanation

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What are the two possible responses a participant can send after receiving a PREPARE message?

a: YES or NO Explanation

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b: COMMIT or ABORT Explanation

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c: VOTE_COMMIT or VOTE_ABORT Explanation

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d: READY or NOT_READY Explanation

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In the simulation, what happens to participants after they vote YES in Phase 1?

a: They immediately commit the transaction Explanation

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b: They enter the PREPARED state and hold locks Explanation

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c: They release all resources and wait Explanation

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d: They send confirmation to other participants Explanation

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What determines whether the coordinator sends GLOBAL_COMMIT or GLOBAL_ABORT in Phase 2?

a: The coordinator's own readiness to commit Explanation

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b: Whether the majority of participants voted to commit Explanation

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c: Whether ALL participants voted to commit Explanation

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d: The priority level of the transaction Explanation

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According to the protocol phases, when do participants release their locks?

a: Immediately after voting in Phase 1 Explanation

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b: When they receive the global decision in Phase 2 Explanation

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c: After executing the commit or abort and sending ACK Explanation

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d: Only when the entire transaction is complete across all nodes Explanation

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In the failure scenario simulation, what causes a transaction to be aborted during Phase 1?

a: Network congestion slowing down messages Explanation

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b: A participant failing before responding to PREPARE Explanation

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c: The coordinator taking too long to make a decision Explanation

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d: Lock contention between concurrent transactions Explanation

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What is the consequence of coordinator failure during Phase 2 (after making the decision)?

a: All participants automatically abort the transaction Explanation

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b: Participants who voted commit remain blocked in PREPARED state Explanation

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c: The transaction outcome depends on which participants received the decision Explanation

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d: A new coordinator must be elected to complete the transaction Explanation

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In the context of recovery, what must a participant do if it finds 'READY' logged in its durable storage after restart?

a: Assume the transaction was aborted and roll back Explanation

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b: Assume the transaction was committed and apply changes Explanation

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c: Contact the coordinator to learn the final decision Explanation

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d: Wait for other participants to contact it with the decision Explanation

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Why is two-phase commit considered a 'blocking' protocol?

a: It blocks other transactions from starting while one is in progress Explanation

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b: Network messages can be blocked by failures or partitions Explanation

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c: Participants in READY state cannot proceed without coordinator contact Explanation

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d: The coordinator blocks until all participants respond Explanation

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