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

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: For each, 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.