Under basic timestamp ordering, transaction T with timestamp 10 tries to read item X whose write timestamp W-TS(X) is 15. What does the protocol do?
Correct answer D. Aborts T and restarts it with a new timestamp
Explanation
Timestamp ordering makes the schedule equivalent to running transactions in timestamp order. X has already been written by a younger transaction (timestamp 15), so T, which is older, would be reading a value from its own future. The read is rejected, and T is aborted and restarted with a new, larger timestamp. Ignoring an operation is allowed only for obsolete writes, under the Thomas write rule.
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