Transactions
Q1.
Which one of the following is NOT a part of the ACID properties of database transactions?Q2.
In a database system, unique time stamps are assigned to each transaction using Lamport's logical clock . Let TS(T_{1}) and TS(T_{2}) be the timestamps of transactions T_{1} and T_{2} respectively. Besides, T_{1} holds a lock on the resource R, and T_{2} has requested a conflicting lock on the same resource R. The following algorithm is used to prevent deadlocks in the database system assuming that a killed transaction is restarted with the same timestamp. Assume any transactions that is not killed terminates eventually. Which of the following is TRUE about the database system that uses the above algorithm to prevent deadlocks?Q3.
Which of the following concurrency control protocol ensures both conflict and free from deadlock? ,Q4.
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(x)R_3(x)R_1(y)W_1(y)W_2 (x)W_3 (y)R_4(y) Which one of the following serial schedules is conflict equivalent to S?Q5.
Suppose a database schedule S involves transactions T1,...,Tn. Construct the precedence graph of S with vertices representing the transactions and edges representing the conflicts. If S is serializable, which one of the following orderings of the vertices of the precedence graph is guaranteed to yield a serial schedule?Q6.
Consider the following two phase locking protocol. Suppose a transaction T accesses (for read or write operations), a certain set of objects {O1,... ,Ok}. This is done in the following manner: Step 1. T acquires exclusive locks to O1,...,Ok in increasing order of their addresses. Step 2. The required operations are performed. Step 3. All locks are released. This protocol willQ7.
Let us assume that transaction T1 has arrived before transaction T2. Consider the schedule s=r1(A);r2(B):w2(A);w1(B)Which of the following is true?Q8.
Consider the following two statements about database transaction schedules: I. Strict two-phase locking protocol generates conflict serializable schedules that are also recoverable. II. Timestamp-ordering concurrency control protocol with Thomas' Write Rule can generate view serializable schedules that are not conflict serializable. Which of the above statements is/are TRUE?Q9.
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.1.T1 start 2.T1 B old =1200 new =100003.T1 M old =0 new =20004.T1 commit5.T2 start6.T2 B old =10000 new =105007.T2 commitSuppose the database system crashes just before log record 7 is written. When the system is restarted, which one statement is true of the recovery procedure?Q10.
Consider the following schedule for transactions T1, T2 and T3: Which one of the schedules below is the correct serialization of the above?