代做COMP9311 24T3: Assignment 2代写留学生Matlab语言

COMP9311 24T3:Assignment 2

Deadline: 5pm Monday Week 10 (11 November)

Note: Please make sure that you always use notations consistent with lecture notes. Different notations will not be accepted.

Question 1 (12 marks)

Consider a relation  R (A, B, C, D, E, G, H, I, J)   and  its  FD  set  F = {AD → B, BD → G, BE → I, AE → DI, AI → E, AEI → C}.

Regarding   the   following    questions,   please    give   your    answers   and   brief justifications.

(1) Check if  AB  → G. (1 mark)

(2) Find all the candidate keys for R. (2 mark)

(3) Determine the highest normal form. of R with respect to F. (2 marks)

(4) Find a minimal cover   Fm    for  F. (2 marks)

(5) Regarding F, does the decomposition R1 = {ABCDJ}, R2 = {BDGI}, R3 = {BCEH} of R satisfy the lossless join property? (2 marks)

(6) Provide a step-by-step lossless decomposition of R into BCNF normal form. (3 marks)

Question 2 (8 marks)

Consider the schedule below. Here, R(*) and W(*) stand for ‘Read’ and ‘Write’, respectively. T1, T2 and T3 represent 3 transactions, and t1, t2, …, t12 represents different timeslots.

Note:  Each  transaction  begins  at  the  time  slot  of  its  first  operation  and commits right after its last operation (same timeslot).

(1) Is the schedule serializable? If it is not serializable, draw a precedence graph; otherwise, provide an equivalent serial schedule. (2 marks)

(2) Use  the Two-Phase  Locking  protocol  to  add  appropriate  locks/unlocks  for each of the transactions. (3 marks)

(3) Based on the locks/unlocks you added in q(2), if the transactions attempt to follow the schedule in the table, what will happen? Please justify your answer using the method learned from the lecture. (3 marks)

Question 3 (6 marks)

Consider the following page request sequence:

P1, P2, P1, P4, P3, P7, P2, P1, P4, P5, P8, P6, P8, P2, P8. Assume there are 3 buffers in the buffer pool.

(1)  Sketch the process of how blocks are replaced in the Least Recently Used (LRU) policy, and calculate the cache hit rate. (2 marks)

(2)  Sketch the process of how blocks are replaced in the Most Recently Used (MRU) policy, and calculate the cache hit rate. (2 marks)

(3)  Sketch the process of how blocks are replaced in the First In First Out (FIFO) policy, and calculate the cache hit rate. (2 marks)