Databases System. The complete book. Exercise 17.2.7. Consider the following sequence of log records: < S,A ,60>; ; < START T>; < T ,A ,

Databases System. The complete book. Exercise 17.2.7. Consider the following sequence of log records:

< S,A ,60>; S>; <START T>; < T ,A , 10>; < START U>; 20>; < T,C , 30>;

V >; 40>; ; ; < T ,E , 50>; ; < V ,B , 80>; V>.

Suppose that we begin a nonquiescent checkpoint immediately after one of the following log records has been written (in memory):

(a) (b) 10> (c)

(d) 40> (e) < T ,E , 50>

The Question: (b only) For (b) 10> tell:

i. When the 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 possible incomplete transactions.

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