Consider the database transactions T 1 and T 2, and data items X and Y . Which of the schedule(s) is/are conflict serializable?

Consider the following read-write schedule $S$ over three transactions $T_{1}$, $T_{2}$, and $T_{3}$, where the subscripts in the schedule indicate transaction IDs:

$S: r_{1}(z); w_{1}(z); r_{2}(x); r_{3}(y); w_{3}(y); r_{2}(y); w_{2}(x); w_{2}(y);$

Which of the following transaction schedules is/are conflict equivalent to $S$?

Let R_i(z) and W_i(z) denote read and write operations on a data element z by a transaction T_i, respectively. Consider the schedule S with four transactions.

S : R₄(x), R₂(x), R₃(x), R₁(y), W₁(y), W₂(x), W₃(y), R₄(y)

Which one of the following serial schedules is conflict equivalent to S?

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?