GATE CS Transactions and Concurrency Control questions

Consider the partial Schedule $S$ involving two transactions $T1$ and $T2$. Only the $\textit{read}$ and the $\textit{write}$ operations have been shown. The $\textit{read}$ operation on data item $P$ is denoted by $\textit{read(P)}$ and $\textit{write}$ operation on data item $P$ is denoted by $\textit{write(P)}$. …

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 of them is conflict serializable?

Consider the following schedule S of transactions $T1, T2, T3, T4:$ …

Consider the transactions $T1, T2, \:\text{and} \:T3$ and the schedules $S1 \:\text{and} \:S2$ given below. $T1: r1(X); r1(Z); w1(X); w1(Z)$ $T2: r2(Y); r2(Z); w2(Z)$ $T3: r3(Y); r3(X); w3(Y)$ $S1: r1(X); r3(Y); r3(X); r2(Y); r2(Z); w3(Y); w2(Z); r1(Z); w1(X); w1(Z)$ $S2: r1(X); r3(Y); r2(Y); r3(X); r1(Z); r2(Z); w3(Y); w1(X); w2(Z); w1(Z)$ …

Consider the following transactions with data items $P$ and $Q$ initialized to zero: …

Consider the following schedule for transactions $T1, T2$ and $T3:$ …

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

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: $T_1: R_1[x]W_1[x]W_1[y]$ $T_2: R_2[x]R_2[y]W_2[y]$ $S_1: R_1[x]R_2[x]R_2[y] W_1[x] W_1[y] W_2[y]$ $S_2: R_1[x]R_2[x]R_2[y] W_1[x] W_2[y] W_1[y]$ $S_3: R_1[x]W_1[x]R_2[x] W_1[y] R_2[y] W_2[y]$ …

Consider the following schedules involving two transactions. Which one of the following statements is TRUE? $S_1 :r_1(X); r_1(Y); r_2(X); r_2(Y); w_2(Y); w_1(X)$ $S_2 :r_1(X); r_2(X); r_2(Y); w_2(Y); r_1(Y); w_1(X)$

Consider the following log sequence of two transactions on a bank account, with initial balance $12000,$ that transfer $2000$ to a mortgage payment and then apply a $5\%$ interest. T1 start T1 B old $=12000$ new $=10000$ T1 M old $=0$ new $=2000$ T1 commit T2 start T2 B old $=10000$ new $=10500$ T2 commit Suppose the database system crashes …

Consider three data items $D1, D2,$ and $D3,$ and the following execution schedule of transactions $T1, T2,$ and $T3.$ In the diagram, $R(D)$ and $W(D)$ denote the actions reading and writing the data item $D$ respectively. …

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

For the schedule given below, which of the following is correct: …