Why the transactions schedule below is violating two- phase policy? Database Concurrency Control Two-Phase Locking Techniques:...

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Why the transactions schedule below is violating two- phase policy? Database Concurrency Control Two-Phase Locking Techniques: The algorithm T1 read_lock (Y); read item (Y); unlock (Y); Time write_lock (X); read item (X); X:=X+Y; write_item (X); unlock (X); T2 read_lock (X); read_item (X): unlock (X); write_lock (Y); read_item (Y); Y:=X+Y; write_item (Y); unlock (Y); Result X=50; Y=50 Nonserializable because it. violated two-phase policy. Why the transactions schedule below is violating two- phase policy? Database Concurrency Control Two-Phase Locking Techniques: The algorithm T1 read_lock (Y); read item (Y); unlock (Y); Time write_lock (X); read item (X); X:=X+Y; write_item (X); unlock (X); T2 read_lock (X); read_item (X): unlock (X); write_lock (Y); read_item (Y); Y:=X+Y; write_item (Y); unlock (Y); Result X=50; Y=50 Nonserializable because it. violated two-phase policy.

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