The wait-die concurrency control is another control that combines the concepts of the immediate-update concurrency control and the timestamp-ordered control.
If transaction T1 makes a request that conflicts with an operation of active
transaction T2
if TS(T1) < TS(T2), then make T1 wait until T2 terminates, else abort T1.
where abort T1 is referred to as a die because T1 kills itself.
a. Showthat the wait-die control serializes in commit order and prevents deadlocks.
b. Compare the fairness of the execution of the kill-wait and wait-die controls.
a. It serializes in commit order because it uses the same locking protocol as the
immediate-update pessimistic control. It prevents deadlocks because a transaction
can only wait for a younger transaction.
b. In the Kill-Wait system the oldest transaction has absolute priority and never waits, but it might kill a transaction that has already been granted permission to perform an operation. In the Wait-Die system, only the requesting transaction is affected by the request.
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