transactions

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...

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...

A schedule of three database transactions $T_1, T_2$, and $T_3$ is shown. $R_i(A)$ and $W_i(A)$ denote read and write of data item $A$ by transaction $T_i, i=1,2,3$. The transactio...

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...

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 : R 4 (x), R 2 (...

Let S be the following schedule of operations of three transactions T 1 , T 2 and T 3 in a relational database system: R 2 (Y), R 1 (X), R 3 (Z), R 1 (Y), W 1 (X), R 2 (Z), W 2 (Y)...

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. S 1 : r 1 (x) r 1 (y) r 2 (x) r...

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...

Consider the following two phase locking protocol. Suppose a transaction $$T$$ accesses (for read or write operations), a certain set of objects $$\left\{ {{O_1},...,{O_k}} \right\...

Suppose a database schedule $$S$$ involves transactions $${T_1},\,...,\,{T_n}.$$ Construct the precedence graph of $$S$$ with vertices representing the transactions and edges repre...

Which one of the following is NOT a part of the $$ACID$$ properties of database transactions?

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 accou...

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)...

Consider the following four schedules due to three transactions (indicated by the subscript) using read and write on a data item x, denoted by r(x) and w(x) respectively. Which one...

Consider the following transactions with data items P and Q initialized to zero: T 1 : read (P) ; read (Q) ; if P = 0 then Q : = Q + 1 ; write (Q). T 2 : read (Q) ; read (P) if Q =...

Consider two transactions T 1 and T 2 and four schedules S 1 , S 2 , S 3 , S 4 of T 1 and T 2 as given below: T 1 : R 1 [ x ] W 1 [ x ] W 1 [ y ] T 2 : R 2 [ x ] R 2 [ y ] W 2 [ y...

Consider the following three schedules of transactions T 1 , T 2 and T 3 . [ Notation: In the following NYO represents the action Y (R for read, W for write) performed by transac­t...

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...

Consider the following schedules involving two transactions. Which one of the following statements is TRUE? S 1 : r 1 (X); r 1 (Y); r 2 (Y); r 2 (X); w 2 (Y); w 1 (X); S 2 : r 1 (X...

Which of the following scenarios may lead to an irrecoverable error in a database system?