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Per WAL semantics, a transaction is officially committed at the moment
Aits `<T commit>` log record is on stable storage
Bits last data page is flushed to disk
Cthe application calls the COMMIT SQL statement
Dall its locks have been released
Answer & Solution
Correct answer: A. its `<T commit>` log record is on stable storage
Commit becomes durable when the commit log record is safely on stable storage. Until that moment, a crash can still undo the transaction. After it, even a crash will redo any pending data-page writes. The data pages themselves can flush asynchronously. The SQL COMMIT call only initiates the log force; it doesn't define the durability point.
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