1、DATABASE MANAGEMENT SYSTEM SAMPLE QUESTIONSQ1.(a) Explain the consistency property of the ACID properties and explain how this property relate to recovery mechanism.(b) Consider the following transaction:Start;Read(X);X: = X+100;Write(X);Read(Y);Y: =Y-100;Write(Y);Commit;(i) During the execution of
2、this transaction, it passes several states until it finally commits. List and explain briefly all the states that this transaction may pass.(ii) If the system fails after operation Y: = Y-100 but not before operation Write(Y), what will happen to this transaction? Explain your answer.Q2.(a) What is
3、a concurrency control? Explain. (c) Consider the following schedule, Schedule S: T1 T2read (P)P = P + 100write (P)read (Q)Q = Q 100write (Q)read (P)P = P * 0.1write (P)read (Q)Q = Q * 0.1write (Q)(i) Write locking and unlocking instructions to the above schedule.(ii) Is the above schedule S conflict
4、 serializable? Show how you derive your answer by using this schedule and explain your answer.Q3.(a) The following concepts are used in recovery. Explain how these concepts can be used in recovery process.(i) transaction log(ii) backup(b) The following questions are based on the following schedule:
5、Time Actiont1 begin At2 begin Bt3 begin Ct4 commit Bt5 checkpoint t6 begin Dt7 commit At8 begin Et9 commit Et10 System crashState which transactions that need to be undone and redone if the following update techniques are used: Deferred update Immediate updateQ4. Explain briefly what discretionary access control is and what are its strength and weakness for data security.
