Database Management System
Q171.
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 willQ172.
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?Q173.
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?Q174.
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?Q175.
Consider the following schedule for transactions T1, T2 and T3: Which one of the schedules below is the correct serialization of the above?Q177.
Consider the following partial Schedule S involving two transactions T1 and T2. Only the read and the write operations have been shown. The read operation on data item P is denoted by read(P) and the write operation on data item P is denoted by write(P). Suppose that the transaction T1 fails immediately after time instance 9. Which one of the following statements is correct?Q179.
Consider a simple checkpointing protocol and the following set of operations in the log. (start, T4); (write, T4, y, 2, 3); (start, T1); (commit, T4); (write, T1, z, 5, 7); (checkpoint); (start, T2); (write, T2, x, 1, 9); (commit, T2); (start, T3), (write, T3, z, 7, 2); If a crash happens now and the system tries to recover using both undo and redo operations, what are the contents of the undo list and the redo list?Q180.
Consider the following schedule S of transactions T1, T2, T3, T4: Which one of the following statements is CORRECT?