Concurrency Control

Consider concurrent execution of two transactions $T 1$ and $T 2$ in a DBMS, both of which access a data object $A$. For these two transactions to not conflict on $A$, which one of...

A schedule of three database transactions T1, T2, and T3 is shown. Ri(A) and Wi(A) denote read and write of data item A by transaction Ti, i = 1,2,3. The transaction T1 aborts at t...

An audit of a banking transactions system has found that on an earlier occasion, two joint holders of account A attempted simultaneous transfers of Rs. 10000 each from account A to...

Consider the database transactions T1 and T2, and data items X and Y. Which of the schedule(s) is/are conflict serializable? Transaction T1 R1(X) W1(Y) R1(X) W1(X) COMMIT(T1) Trans...

Which of the following statements about the Two Phase Locking (2PL) protocol is/are TRUE?

Consider the following read-write schedule S over three transactions T1, T2, and T3, where the subscripts in the schedule indicate transaction IDs: S: r₁(z); w₁(z); r₂(x); r₃(y); w...

Which of the following statements about the Two Phase Locking (2PL) protocol is/are TRUE?

Consider the following two statements about database transaction schedules: I. Strict two-phase locking protocol generates conflict serializable schedules that are also recoverable...

Two transactions T₁ and T₂ are given as T1:r1(X)w1(X)r1(Y)w1(Y) T2:r2(Y)w2(Y)r2(Z)w2(Z) where ri (V) denotes a read operation by transaction Tᵢ on a variable V and wᵢ(V) denotes a...

Which of the following concurrency control protocols ensure both conflict serializability and freedom from deadlock? I. 2-phase locking II. Time-stamp ordering

Consider the following two transactions: T 1 and T 2 . T 1 : read (A); T 2 : read (B); read (B); read (A); if A = 0 then B ← B + 1; if B ≠ 0 then A ← A - 1; write (B); write (A); W...