# Assignment5a - Pages 638-9: Exercises 17.14 Discuss the...

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Pages 638-9: Exercises 17.14 Discuss the final result of the different schedules in Figure 17.3(a) and (b), where M = 2 and N = 2, with respect to the following questions. Does adding the above condition change the final outcome? Does the outcome obey the implied consistency rule (that the capacity of X is 90)? As long as the initial value isn’t X>88, the condition doesn’t change the outcome. The value of X isn’t updated if the value is greater than 90 so as long as the value of x<90, it does obey the implied consistency rule. Pages 638-9: Exercises 17.16 Add the operation commit at the end of each of the transactions T 1 and T 2 from Figure 17.2; then list all possible schedules for the modified transactions. Determine which of the schedules are recoverable, which are cascadeless, and which are strict. T 1 T 2 read_item(X); read_item(X); X := X - N; X := X + M; write_item(X); write_item(X); read_item(Y); commit T 2 Y := Y + N; write_item(Y); commit T 1 Shorthand notation: T 1 : r 1 (X); w 1 (X); r 1 (Y); w 1 (Y); C 1 ; T 2 : r 2 (X); w 2 (X); C 2 ; In this case, m=2 (T 1 and T 2 ) and n 1 = 5 and n 2 = 3. The number of possible schedules is: 8!/(5!*3!) = 40320/720 = 56 Recoverable = after T is committed, never be necessary rolled back Non-Recoverable = after T is committed, rolled back Cascadeless = every transaction is only read by committed transactions. Strict = never read or written (x) until the last T(x) is committed. The following listing is all 56 possible schedules and which are recoverable, which are cascadeless, and which are strict. S 1 : r 1 (X); w 1 (X); r 1 (Y); w 1 (Y); C 1 ; r 2 (X); w 2 (X); C 2 ; strict S 2 : r 1 (X); w 1 (X); r 1 (Y); w 1 (Y); r 2 (X); C 1 ; w 2 (X); C 2 ; recoverable S 3 : r 1 (X); w 1 (X); r 1 (Y); w 1 (Y); r 2 (X); w 2 (X); C 1 ; C 2 ; recoverable S 4 : r 1 (X); w 1 (X); r 1 (Y); w 1 (Y); r 2 (X); w 2 (X); C 2 ; C 1 ; non-recoverable S 5 : r 1 (X); w 1 (X); r 1 (Y); r 2 (X); w 1 (Y); C 1 ; w 2 (X); C 2 ; recoverable S 6 : r 1 (X); w 1 (X); r 1 (Y); r 2 (X); w 1 (Y); w 2 (X); C 1 ; C 2 ; recoverable

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S 7 : r 1 (X); w 1 (X); r 1 (Y); r 2 (X); w 1 (Y); w 2 (X); C 2 ; C 1 ; non-recoverable S 8 : r 1 (X); w 1 (X); r 1 (Y); r 2 (X); w 2 (X); w 1 (Y); C 1 ; C 2 ; recoverable S 9 : r 1 (X); w 1 (X); r 1 (Y); r 2 (X); w 2 (X); w 1 (Y); C 2 ; C 1 ; non-recoverable S 10 : r 1 (X); w 1 (X); r 1 (Y); r 2 (X); w 2 (X); C 2 ; w 1 (Y); C 1 ; non-recoverable S 11 : r 1 (X); w 1 (X); r 2 (X); r 1 (Y); w 1 (Y); C 1 ; w 2 (X); C 2 ; recoverable S 12 : r 1 (X); w 1 (X); r 2 (X); r 1 (Y); w 1 (Y); w 2 (X); C 1 ; C 2 ; recoverable S 13 : r 1 (X); w 1 (X); r 2 (X); r 1 (Y); w 1 (Y); w 2 (X); C 2 ; C 1 ; non-recoverable S 14 : r 1 (X); w 1 (X); r 2 (X); r 1 (Y); w 2 (X); w 1 (Y); C 1 ; C 2 ; recoverable S 15 : r 1 (X); w 1 (X); r 2 (X); r 1 (Y); w 2 (X); w 1 (Y); C 2 ; C 1 ; non-recoverable S 16 : r 1 (X); w 1 (X); r 2 (X); r 1 (Y); w 2 (X); C 2 ; w 1 (Y); C 1 ; non-recoverable S 17 : r 1 (X); w 1 (X); r 2 (X); w 2 (X); r 1 (Y); w
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## This note was uploaded on 09/07/2011 for the course MIS unknown taught by Professor Unknown during the Fall '09 term at New York Institute of Technology-Westbury.

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Assignment5a - Pages 638-9: Exercises 17.14 Discuss the...

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