Due November 28 beginning of class
(Late homework will not be accepted; all homework must be done independently)
Following problems are from Ullman Text.
Page 535: 9.1, 9.2, 9.3
Page 536: 9.6, 9.7
Page 539: 9.23, 9.26
Problem: Consider the following two transactions:
T1 : read(A);
read(B);
if A = 0 then B := B + 1;
write(B).
T2 : read(B);
read(A);
if B = 0 then A := A + 1;
write(A).
Let the consistency requirement be A = 0 OR B = 0, with A = B = 0 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 T1 and T2 that produces a nonserializable schedule.
(c) Is there a concurrent execution of T1 and T2 that
produces a serializable schedule.