Consider the following statements: Statement I: Conservative 2 PL is a deadlock-free protocol. Statement II: Thomas's write rule enforces conflict serializability. Statement III: Timestamp ordering protocol ensures serializability based on the order of transaction timestamps. Which of the following is correct?
Statement I, Statement III true and Statement II false
Statements I and III are true; II is false. Conservative two-phase locking obtains all required locks before execution, avoiding hold-and-wait deadlock. Basic timestamp ordering serializes transactions in timestamp order. Thomas’s write rule can admit view-serializable schedules that are not conflict-serializable.
Important Questions from Serializability of Schedules - Teaching
Suppose a database schedule 5 involves transactions T 1, T 2, .............T nConsider the precedence graph of S with vertices representing the transactions and edges representing the conflicts. If S is serializable, which one of the following orderings of the vertices of the precedence graph is guaranteed to yield a serial schedule ?
Consider the following schedules involving two transactions.
S 1: 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 statements is correct with respect to above?Consider the following schedule S.
T1 T2 T3 T4 Timestamp R(X) R(Y) t1 W(X) W(Y) t2 R(Y) R(X) t3 W(Y) W(X) t4 R(X) t5 W(X) t6 R(X) denotes read operation on data item X by transaction Ti.
W(X) denotes write operation on data item X by transaction Ti.
Choose the correct execution order for the above schedule S.
Consider the transactions T1, T2, T3 and the schedules S1 and S2 given below.
T1 : r1(x); r1(z); w1(z)
T2 : r2(y); r2(z); w2(z)
T3 : r3(y); r3(x); w3(y)
S1 : r1(x); r3(y); r3(x); r2(y); r2(z); w3(y); w3(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 ?
Consider following schedules involving two transactions :
S1 : r1(X); r1(Y); r2(X); r2(Y); w2(Y); w1(X)
S2 : r1(X); r2(X); r2(Y); w2(Y); r1(Y); w1(X)
Which of the following statement is true ?
