In: Computer Science
Which of these statements about deadlock are true? (list all
that are true.)
a. If all transactions use two-phase locking, they cannot
deadlock.
b. Once two transactions deadlock, one of them must be aborted to
maintain correctness.
c. Systems that support update locks (S, X and U modes) cannot
deadlock.
d. Validation based concurrency control schemes cannot
deadlock.
ANSWERS -
The correct statements about deadlock are -
(b) To maintain correctness one of the two transaction must be terminated or aborted.
For maintaining accuracy one of the transaction must be terminated so that the other transaction can proceed with execution without deadlock.
(d) Deadlock doesn't occur in validation based concurrency control
Validation based concurrency control ensures that two transaction does not conflict ensuring the execution thus avoiding deadlock.
Two phase locking ensures serializability but doesn't avoid the deadlock situation. So, this statement is false.
Update lock supported system can also get into deadlock. So, this statement is also false.
So, the correct options related to deadlock are (b) and (d).
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