Virtual Labs

2-Phase Commit Protocol Simulation

What is the primary purpose of the Two-Phase Commit (2PC) protocol?

a: To ensure high availability of services Explanation

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b: To achieve consensus on transaction atomicity in distributed systems Explanation

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c: To encrypt data during transmission Explanation

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d: To reduce network latency Explanation

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In which phase of 2PC does the coordinator ask participants if they are ready to commit?

a: The Decision Phase Explanation

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b: The Commit Phase Explanation

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c: The Voting Phase Explanation

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d: The Acknowledgment Phase Explanation

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What message does a participant send if it is ready to commit?

a: YES Explanation

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b: VOTE_COMMIT Explanation

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c: READY Explanation

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d: ACK Explanation

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What happens if the coordinator receives at least one `VOTE_ABORT` message?

a: It asks the participant to vote again. Explanation

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b: It commits the transaction for the other participants. Explanation

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c: It sends a `GLOBAL_ABORT` message to all participants. Explanation

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d: It waits for more votes to form a majority. Explanation

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Why must a participant write 'READY' to a durable log before sending `VOTE_COMMIT`?

a: To prove to the coordinator that it is not busy. Explanation

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b: To have a record of its vote in case it crashes and recovers. Explanation

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c: To timestamp the beginning of the transaction. Explanation

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d: To let other participants know its status. Explanation

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If a coordinator fails before sending any decision messages, what is the state of a participant that voted `VOTE_COMMIT`?

a: It automatically commits after a timeout. Explanation

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b: It automatically aborts after a timeout. Explanation

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c: It is blocked and cannot proceed until the coordinator recovers. Explanation

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d: It asks other participants for the decision. Explanation

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Which of the following scenarios is the primary cause of the 'blocking problem' in 2PC?

a: A participant fails before voting. Explanation

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b: A participant fails after voting to abort. Explanation

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c: The coordinator fails after sending `PREPARE` but before sending the final decision. Explanation

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d: The network connection between two participants is lost. Explanation

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How does the 'Presumed Abort' optimization work in 2PC?

a: The coordinator presumes all participants will abort and doesn't send a `PREPARE` message. Explanation

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b: Participants that don't receive a vote request within a certain time automatically abort. Explanation

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c: The coordinator and participants do not need to write `ABORT` records to their logs. Explanation

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d: The coordinator presumes a commit vote unless it explicitly receives an abort vote. Explanation

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Why is Three-Phase Commit (3PC) considered non-blocking compared to 2PC?

a: It eliminates the coordinator. Explanation

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b: It adds a 'pre-commit' phase that allows participants to reach consensus if the coordinator fails. Explanation

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c: It uses fewer messages, reducing the chance of network failure. Explanation

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d: It does not require durable logging, making it faster. Explanation

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