Two concurrent global transactions, T1 and T2, consist of the following: T1 = {rl (x1), rl...

  

Transcribed Image Text:

Two concurrent global transactions, T1 and T2, consist of the following: T1 = {rl (x1), rl (x5), w1(x1), r1(x6), w1(x5), w1(x6), r1(x2), w1(x2)} T2 = {r2(x3), w2(x3), 12(x4), w2(x4), r2(x6), w2(x6)} where ri(xi) and wi(xj) denote a read and a write operation by transaction i on data item xj. Data items x1, x3 and x5 are stored at site A, while x2, x4 and x6 are stored at site B. In addition, two local transactions L3 and L4 consist of the following: L3 = {r3(x1), r3(x5), w3(x1), r3(x3), w3(x5), w3(x3)} at site A L4= {r4(x2), r4(x6), w4(x2), r4(x4)} at site B and they are executed concurrently with T1 and T2. 2A. (2pts) 1). How many serial schedules of these 18 actions are there in T1, T2 and L4? (1 pt) 2). How many possible schedules of these 10 actions are there in L3 and L4? (1 pt) 2B. (9 pts) Suppose that the schedules SA and SB produced by the local schedulers at site A and site B respectively are as follows: SA = {r3(x1), r3(x5), w3(x1), r1(x1), r1(x5), w1(x1), r2(x3), w2(x3), r3(x3), w3(x3)} SB = {r1(x6), r4(x2), r1(x2), w4(x2), r2(x4), w2(x4), r4(x4), r2(x6), w2(x6)} Two concurrent global transactions, T1 and T2, consist of the following: T1 = {rl (x1), rl (x5), w1(x1), r1(x6), w1(x5), w1(x6), r1(x2), w1(x2)} T2 = {r2(x3), w2(x3), 12(x4), w2(x4), r2(x6), w2(x6)} where ri(xi) and wi(xj) denote a read and a write operation by transaction i on data item xj. Data items x1, x3 and x5 are stored at site A, while x2, x4 and x6 are stored at site B. In addition, two local transactions L3 and L4 consist of the following: L3 = {r3(x1), r3(x5), w3(x1), r3(x3), w3(x5), w3(x3)} at site A L4= {r4(x2), r4(x6), w4(x2), r4(x4)} at site B and they are executed concurrently with T1 and T2. 2A. (2pts) 1). How many serial schedules of these 18 actions are there in T1, T2 and L4? (1 pt) 2). How many possible schedules of these 10 actions are there in L3 and L4? (1 pt) 2B. (9 pts) Suppose that the schedules SA and SB produced by the local schedulers at site A and site B respectively are as follows: SA = {r3(x1), r3(x5), w3(x1), r1(x1), r1(x5), w1(x1), r2(x3), w2(x3), r3(x3), w3(x3)} SB = {r1(x6), r4(x2), r1(x2), w4(x2), r2(x4), w2(x4), r4(x4), r2(x6), w2(x6)}