Let S be the following schedule of operations of three transactions T₁, T₂ and T₃ in a relational database system:

R₂(Y), R₁(X), R₃(Z), R₁(Y), W₁(X), R₂(Z), W₂(Y), R₃(X), W₃(Z)

Consider the statements P and Q below:

P: S is conflict-serializable.

Q: If T₃ commits before T₁ finishes, then S is recoverable.

Which one of the following choices is correct?

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 : 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 one of the following options is correct?

Consider a schedule of transactions T₁ and T₂ :
Here, RX stands for “Read(X)” and WX stands for “Write(X)”. Which one of the following schedules is conflict equivalent to the above schedule?

Consider the following database schedule with two transactions, T₁ and T₂

 S = r2(X); r1(X); r2(Y); w1(X); r1(Y); w2(X); a1; a2

where r_i(Z) denotes a read operation by transaction T_i on a variable Z, w_i(Z) denotes a write operation by T_i on a variable Z and a_i denotes an abort by transaction T_i .

Which one of the following statements about the above schedule is TRUE?