Consider the following two transactions: (SHOW WORK) T13: read(A); read(B); if A = 1 then B := B - 1; write(B). T14: read(B); read(A); if B = 1 then A := A - 1; write(A). Let the consistency requirement be A = 1 or B = 1, with A = 1 and B = 1 as the initial values.a. Show that every serial execution involving these two transactions preserves the consistency of the database.b. Show a concurrent execution of T13 and T14 that produces a nonserializable schedule.c. Is there a concurrent execution of T13 and T14 that produces a serializable schedule?
Consider the following two transactions: (SHOW WORK) T13: read(A); read(B); if A = 1 then B := B - 1; write(B). T14: read(B); read(A); if B = 1 then A := A - 1; write(A). Let the consistency requirement be A = 1 or B = 1, with A = 1 and B = 1 as the initial values.a. Show that every serial execution involving these two transactions preserves the consistency of the database.b. Show a concurrent execution of T13 and T14 that produces a nonserializable schedule.c. Is there a concurrent execution of T13 and T14 that produces a serializable schedule?
Database Systems: Design, Implementation, & Management
12th Edition
ISBN:9781305627482
Author:Carlos Coronel, Steven Morris
Publisher:Carlos Coronel, Steven Morris
Chapter10: Transaction Management And Concurrency Control
Section: Chapter Questions
Problem 7P
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Consider the following two transactions: (SHOW WORK)
T13: read(A); read(B);
if A = 1 then B := B - 1; write(B).
T14: read(B); read(A);
if B = 1 then A := A - 1;
write(A).
Let the consistency requirement be A = 1 or B = 1, with A = 1 and B = 1 as the initial values.
a. Show that every serial execution involving these two transactions preserves the consistency of the database.
b. Show a concurrent execution of T13 and T14 that produces a nonserializable schedule.
c. Is there a concurrent execution of T13 and T14 that produces a serializable schedule?
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