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Ex.4

For each of the schedules of transactions T1, T2, and T3 below:

1. r1(A); r2(B); r3(C); r1(B); r2(C); r3(D); w1(A); w2(B); w3(C);
2. r1(A); r2(B); r3(C); r1(B); r2(C); r3(A); w1(A); w2(B); w3(C);

do each of the following:

ii) Insert shared and exclusive locks in a way that allows upgrading. Place a shared lock in front of every read, an exclusive lock in front of every write, and place the necessary unlocks at the ends of the transactions.
Tell what happens when each schedule is run by a scheduler that supports shared locks, exclusive locks, and upgrading.
iii) Insert shared, exclusive, and update locks, along with unlock actions. Place a shared lock in front of every read action that is not going to be upgraded, place an update lock in front of every read action that will be upgraded, and place an exclusive lock in front of every write action. Place unlocks at the ends of transactions, as usual.
Tell what happens when each schedule is run by a scheduler that supports shared, exclusive, and update locks.

Ex.5

Consider the following sequence of UNDO log records:
[START S]
[S,A,60]
[COMMIT S]
[START T]
[T,A,10]
[START U]
[U,B,20]
[T,C,30]
[START V]
[U,D,40]
[V,F,70]
[COMMIT U]
[T,E,50]
[COMMIT T]
[V,B,80]
[COMMIT V]
Suppose that we begin a nonquiscent checkpoint immediately after one of the following log records has written (in memory):
a) [S,A,60]
b) [T,A,10]
c) [U,B,20]
d) [U,D,40]
e) [T,E,50]
For each, tell:
i) When the [END CKPT] record is written, and
ii) For each possible point at which a crash could occur, how far back in the log we must look to find all the possible incomplete transactions.

Ex.6

Consider the previous exercise, but interpret the log as a REDO log.
For each (a,b,c,d,f), tell:
i) At what points could the [END CKPT] record be written, and
ii) For each possible point at which a crash could occur, how far back in the log we must look to find all the possible incomplete transactions. Consider both the case that the [END CKPT] record was or was not written prior to the crash.

Ex.7

For each of the following relation schemas and sets of FD’s:
a) R(A,B,C,D) with FD’s AB→C, B→D, CD→A, AD→B.
b) R(A,B,C,D) with FD’s A→B, B→C, C→D, D→A.
Indicate the BCNF violations (if any). Decompose the relations, as necessary, into relations that are in BCNF.

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在此对LE PHUONG对本文所作的贡献表示诚挚感谢，她在山东大学完成了计算机科学与技术专业的硕士学位，专注数据分析、数据可视化、数据采集等。擅长Python、SQL、C/C++、HTML、CSS、VSCode、Linux、Jupyter Notebook。