Transaction isolation levels: 3.1) Consider the following Account table Assume t

Question

Transaction isolation levels:

3.1) Consider the following Account table

Assume the following two transactions are submitted:

T1: adds $1000 to account 1

T2: makes account 2 balance equals to account 1 balance

a) What are the final database contents for each of the following possible scenarios

b) What are the final database contents after executing the following schedule for each of the following isolation levels? Explain why or why not the two isolation levels results in different final values in the database.

accNum bal 1 1000 2 0

Explanation / Answer

a)

b)

for T1 bal = 1000

for T2 bal = 1000

for T1 bal = 0

for T2 bal = 0

for T1 bal = 2000

for T2 bal = 2000

for T1 bal = 0

for T2 bal = 2000

for T1 bal = 1000

for T2 bal = 1000

for T1 bal = 0

for T2 bal = 0

accNum 1 accNum 2 Neither transaction completes its work 1000 0 Only T1 completes its work 2000 0 Only T2 completes its work 1000 1000 Serial execution T1 T2 2000 2000 Serial execution T2 T1 2000 1000

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