GATE CSE
Database Management System
Transactions and Concurrency
Previous Years Questions

Marks 1

Let Ri(z) and Wi(z) denote reac and write operations on a data element z by a transaction Ti, respectively. Consider the schedule S with four transact...
Consider the following two statements about database transaction schedules: I. Strict two-phase locking protocol generates conflict serializable sche...
Suppose a database schedule $$S$$ involves transactions $${T_1},\,...,\,{T_n}.$$ Construct the precedence graph of $$S$$ with vertices representing th...
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 con...
Which of the following concurrency control protocols ensure both conflict serializability and freedom from deadlock? I. 2-phase locking II. Time-sta...
Amongst the ACID properties of a transaction, the 'Durability' property requires that the changes made to the database by a successful transaction per...
Which level of locking provides the highest degree of concurrency in a relational database?
Which of the following scenarios may lead to an irrecoverable error in a database system?

Marks 2

Suppose a database system crashes again while recovering from a previous crash. Assume checkpointing is not done by the database either during the tra...
Let ri(z) and wi(z) denote read and write operations respectively on a data item z by a transaction Ti. Consider the following two schedules. S1 : r1...
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 c...
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 ri(Z) ...
Consider the following two phase locking protocol. Suppose a transaction $$T$$ accesses (for read or write operations), a certain set of objects $$\le...
Consider a simple checkpointing protocol and the following set of operations in the log. (start, $$T4$$); (write, $$T4, y, 2, 3$$); (start, $$T1$$); ...
Consider the following partial Schedule S involving two transactions $$T1$$ and $$T2.$$ Only the read and the write operations have been shown. The re...
Consider the following four schedules due to three transactions (indicated by the subscript) using read and write on a data item x, denoted by r(x) an...
Consider the transactions T1, T2, and T3 and the schedules S1 and S2 given below. T1 : r1 (X) ; r1 (Z) ; w1 (X) ; w1 (Z) T2 : r2 (X) ; r2 (Z) ; w2 (Z...
Consider the following schedule S of transactions T1, T2, T3, T4: ...
Consider the following transactions with data items P and Q initialized to zero: T1 : read (P) ; read (Q) ; if P = 0 then Q : = Q + 1 ; ...
Consider the following schedule for transactions T1, T2 and T3: Which one of the schedules below is the correct serialization of the above?...
Consider two transactions T1 and T2 and four schedules S1, S2, S3, S4 of T1 and T2 as given below: T1: R1[ x ] W1[ x ] W1[ y ] T2: R2[ x ] R2[ y ] W...
Let R and S be relational schemes such that R = { a, b, c } and S = { c }. Now consider the following queries on the database: I. $$\pi_{R-S}(r) - \pi...
Consider the following three schedules of transactions T1, T2 and T3. [ Notation: In the following NYO represents the action Y (R for read, W for writ...
Consider the following schedules involving two transactions. Which one of the following statements is TRUE? S1: r1(X); r1(Y); r2(Y); r2(X); w2(Y); w1...
Consider the following two transactions: T1 and T2. T1: read (A); T2: read (B); read (B); read (A); if A...
Consider the following schedule S of transactions T1 and T2: Which of the following is TRUE about the schedule S?...
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 th...
For the schedule given below, which of the following is correct: ...
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