Transactions and concurrency control

Question 41

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

• I only

• II only

• Both I and II

• Neither I nor II

Question 42

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 ;
    write (Q) ;
T2: read (Q) ;
    read (P) ;
    if Q = 0 then P : = P + 1 ;
    write (P) ;

Any non-serial interleaving of T1 and T2 for concurrent execution leads to

• A serializable schedule

• A schedule that is not conflict serializable

• A conflict serializable schedule

• A schedule for which a precedence graph cannot be drawn

Question 43

Assume the following information: Original timestamp value = 46 Receive timestamp value = 59 Transmit timestamp value = 60 Timestamp at arrival of packet = 69 Which of the following statements is correct?

• Receive clock should go back by 3 milliseconds
• Transmit and Receive clocks are synchronized
• Transmit clock should go back by 3 milliseconds
• Receive clock should go ahead by 1 milliseconds

Question 44

Suppose a database system crashes again while recovering from a previous crash. Assume checkpointing is not done by the database either during the transactions or during recovery. Which of the following statements is/are correct?

• The same undo and redo list will be used while recovering again
• The system cannot recover any further
• All the transactions that are already undone and redone will not be recovered again
• The database will become inconsistent

Question 45

__________ rules used to limit the volume of log information that has to be handled and processed in the event of system failure involving the loss of volatile information.

• Write-ahead log

• Check-pointing

• Log buffer

• Thomas

Question 46

Which of the following RAID level provides the highest Data Transfer Rate (Read/Write)

• RAID 1
• RAID 3
• RAID 4
• RAID 5

Question 47

What is the equivalent serial schedule for the following transactions?

T1          T2          T3
                       R(Y)
                       R(Z)
R(X)
W(X) 
                       W(Y)
                       W(Z)
           W(Z)
R(Y)
W(Y) 
           R(Y)
           W(Y)
           R(X)
           W(X)                                

• T1 − T2 − T3
• T3 − T1 − T2
• T2 − T1 − T3
• T1 − T3 − T2

Question 48

Which of the following is the highest isolation level in transaction management?

• Serializable
• Repeated Read
• Committed Read
• Uncommitted Read