Repeat Exercise 20.14, adding a check in T 1 so that Y does not exceed 90. Exercise

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Repeat Exercise 20.14, adding a check in T1 so that Y does not exceed 90.


Exercise 20.14

Change transaction T2 in Figure 20.2(b) to read

read_item(X);
X := X + M;
if X > 90 then exit
else write_item(X);

Discuss the final result of the different schedules in Figures 20.3(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)?


Figures 20.3(a) and (b):


Figure 20.2(b)

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Fundamentals Of Database Systems

ISBN: 9780133970777

7th Edition

Authors: Ramez Elmasri, Shamkant Navathe

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