Question

PART II: Transactions (10 pts) Find if there exist any anomalies in the following schedules. Specify the type of anomalies found (if any). Show where in the schedule anomalies exist. a) Consider the following interleaved execution of three transactions, and let the initial values be as follows: x=10, y=20, z=30. (i) Is there any problem with this concurrent execution of the three transactions? Explain why or why not? What will be the final values of x, y, and z in the database? T1 T2 T3 1 Read(x) 2 Read(y) 3 y = y - x 4 Read(x) 5 x = x + 10 6 Read(z) 7 Write(x) 8 Write(y) 9 z = 2 * z 10 Write(z) 11 Read(z) 12 z = y + z 13 Write(z) b) Consider the following interleaved execution of three transactions. Should the system then abort T1 as well? Explain why or why not. If the initial values be as follows: x=10, y=20, z=30, what will be the final values in the database? T1 T2 T3 1 Read(x) 2 Read(y) 3 y = y - x 4 Read(x) 5 x = x + 10 6 Read(z) 7 Write(x) 8 Write(y) 9 z = 2 * z 10 Write(z) 11 Read(y) 12 y = y + z 13 Write(y) 14 Abort

          PART II: Transactions (10 pts)
Find if there exist any anomalies in the following schedules. Specify the type of
anomalies found (if any). Show where in the schedule anomalies exist.
a) Consider the following interleaved execution of three transactions, and let the
initial values be as follows: x=10, y=20, z=30. (i) Is there any problem with this
concurrent execution of the three transactions? Explain why or why not? What
will be the final values of x, y, and z in the database?
T1
T2
T3
1 Read(x)
2 Read(y)
3 y = y - x
4
Read(x)
5
x = x + 10
6
Read(z)
7
Write(x)
8 Write(y)
9
z = 2 * z
10
Write(z)
11 Read(z)
12 z = y + z
13 Write(z)
b) Consider the following interleaved execution of three transactions. Should the
system then abort T1 as well? Explain why or why not. If the initial values be as
follows: x=10, y=20, z=30, what will be the final values in the database?
T1
T2
T3
1 Read(x)
2 Read(y)
3 y = y - x
4
Read(x)
5
x = x + 10
6
Read(z)
7
Write(x)
8 Write(y)
9
z = 2 * z
10
Write(z)
11
Read(y)
12
y = y + z
13
Write(y)
14
Abort

PART II: Transactions (10 pts)
Find if there exist any anomalies in the following schedules. Specify the type of
anomalies found (if any). Show where in the schedule anomalies exist.
a) Consider the following interleaved execution of three transactions, and let the
initial values be as follows: x=10, y=20, z=30. (i) Is there any problem with this
concurrent execution of the three transactions? Explain why or why not? What
will be the final values of x, y, and z in the database?
T1
T2
T3
1 Read(x)
2 Read(y)
3 y = y - x
4
Read(x)
5
x = x + 10
6
Read(z)
7
Write(x)
8 Write(y)
9
z = 2 * z
10
Write(z)
11 Read(z)
12 z = y + z
13 Write(z)
b) Consider the following interleaved execution of three transactions. Should the
system then abort T1 as well? Explain why or why not. If the initial values be as
follows: x=10, y=20, z=30, what will be the final values in the database?
T1
T2
T3
1 Read(x)
2 Read(y)
3 y = y - x
4
Read(x)
5
x = x + 10
6
Read(z)
7
Write(x)
8 Write(y)
9
z = 2 * z
10
Write(z)
11
Read(y)
12
y = y + z
13
Write(y)
14
Abort

Added by Ronnie P.

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