GATE PYQ

Transactions

Q31.
Which of the following is the highest isolation level in transaction management?

Q32.
Consider the following partial Schedule S involving two transactions T1 and T2. Only the read and the write operations have been shown. The read operation on data item P is denoted by read(P) and the write operation on data item P is denoted by write(P). Suppose that the transaction T1 fails immediately after time instance 9. Which one of the following statements is correct?

Q33.
What is the equivalent serial schedule for the following transactions?

Q34.
Consider a simple checkpointing protocol and the following set of operations in the log. (start, T4); (write, T4, y, 2, 3); (start, T1); (commit, T4); (write, T1, z, 5, 7); (checkpoint); (start, T2); (write, T2, x, 1, 9); (commit, T2); (start, T3), (write, T3, z, 7, 2); If a crash happens now and the system tries to recover using both undo and redo operations, what are the contents of the undo list and the redo list?

Q35.
Consider the following schedule S of transactions T1, T2, T3, T4: Which one of the following statements is CORRECT?

Q36.
Consider the following transactions with data items P and Q initialized to zero: T1 :read (P); read (Q); if P = 0 then Q := Q + 1 ; write (Q). T2 : read (Q); read (P); if Q = 0 then P := P + 1 ; write (P). Any non-serial interleaving of T1 and T2 for concurrent execution leads to

Q37.
Consider the transactions T1, T2, and T3 and the schedules S1 and S2 given below. T1 : r1(x); r1(Z) ; w1(x); w1(Z) T2 : r2(x); r2(Z); w2(Z) T3 : r3(x); r3(x); w3(Y) S1: r1(x); r3(Y); r3(x); r2(Y); r2(Z); w3(Y); w2(Z); r1(Z); w1(x); w1(Z) S2: r1(x); r3(Y); r2(Y); r3(x); r1(Z); r2(Z); w3(Y); w1(x); w2(Z); w1(Z) Which one of the following statements about the schedules is TRUE?

Q38.
Consider the following four schedules due to three transactions (indicted by the subscript) using read and write on a data item x, denoted by r(x) and w(x) respectively. Which one of them is conflict serializable?

Q39.
Consider the following transaction involving two bank accounts x and y. read(x); x:=x-50; write(x); read(y); y:=y+50; write(y) The constraint that the sum of the accounts x and y should remain constant is that of

Q40.
Let r_i(z) and w_i(z) denote read and write operations respectively on a data item z by a transaction T_i. Consider the following two schedules. S1: r_1(x)r_1(y)r_2(x)r_2(y)w_2(y)w_1(x) S2: r_1(x)r_2(x)r_2(y)w_2(y)r_1(y)w_1(x) Which one of the following options is correct?