Give examples of schedules that would be accepted at
a. SNAPSHOT isolation but not REPEATABLE READ.
b. SERIALIZABLE but not SNAPSHOT isolation. (Hint: T2 performs a write after T1 has committed.)
a. r1(x) r1(y) w1(x) r2(y) r2(x) w1(y) commit2 commit1
A deadlock would occur at REPEATABLE READ.
b. r1(x) r1(y) r2(y) w1(x) commit1 r2(x) w2(x) commit2
This schedule is serializable, but would not be allowed in SNAPSHOT isolation, because both concurrent transactions updated x.
Computer Science & Information Technology
You might also like to view...
A unique mathematical __________ is input into the encryption algorithm to lock down the data by creating the ciphertext.
Fill in the blank(s) with the appropriate word(s).
Computer Science & Information Technology
In a(n) ____________________ structure, one of two branches of logic is followed based on a decision.
Fill in the blank(s) with the appropriate word(s).
Computer Science & Information Technology