1. Scenario A
(1)隔离等级太低，会导致别的事务影响数据
(2)事物太长，包括了与用户的交互，会导致其他用户等待时间过长
(3)结果信息的展示应当放在 commit 或者 rollback 后
2. Scenario B
隔离等级不对，事务仍过长包括了用户交互
3. Scenario C
事务还是包括了交互
4．Correct One
William
Julie
ATM prompts user for
operation.
ATM Prompts user for
operation.
William Chooses Deposit into
Savings.
Julie Chooses Deposit into
Checking.
ATM prompts user for amount.
ATM Prompts user for amount.
William enters 400.
Julie enters 500.
▪ Begin
transaction
(serializable isolation
level)
▪ Begin
transaction
(serializable isolation
level)
▪ Select
balance of savings
▪ Select
balance of checking
savings_balance =
savings_balance $400
checking_balance =
checking_balance $500
▪ Update
savings balance in
database.
▪ Update
checking balance in
database.
▪ End
Transaction
▪ End
Transaction
