In each of the following cases, state (yes or no) whether the resulting schedule is always serializable and recoverable. If the answer is no, give an example of a schedule that is either not serializable or not recoverable.
Two transactions run concurrently, and each might either commit or abort. The transactions are chosen from the following:
T1 : r1(x) w1(y)
T2 : w2(x)
T3 : r3(y) w3(x)
T4 : r4(x) w4(x) w4(y)
a. T1 and T2 both running at READ UNCOMMITTED
b. T2 and T2 both running at READ UNCOMMITTED
c. T1 and T2 both running at READ COMMITTED
d. T1 and T3 both running at READ COMMITTED
e. T1 and T3 both running at SNAPSHOT isolation
f. T1 and T4 both running at SNAPSHOT isolation
a. No.
w2(x) r1(x) w1(y) c1 a2
Not recoverable
b. Yes
c. Yes
d. No
r1(x) r3(y) w1(y) w3(x)
Not serializable
e. No
r1(x) r3(y) w1(y) w3(x)
Not serializable
f. Yes
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