Free Transactions and concurrency lessonsTransactions and concurrency · Stage 2 · Control and recovery · Step 1
Locks and two-phase locking
See how shared and exclusive locks, taken in two phases, guarantee serializable schedules. About 14 minutes.
Which of these breaks the rule of two-phase locking?
- AA transaction releases a lock and then acquires a new lock
- BA transaction acquires many locks one after another
- CTwo transactions hold shared locks on the same item
Show the answer
A transaction releases a lock and then acquires a new lock. Once it has entered the shrinking phase, it may only release.
4 questions on this idea
Short questions that apply the idea to new cases: trace it, work out a number, put steps in order. A wrong answer explains itself.
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