Tale Of Two Transactions

• T1: Deposit $100 T2: Withdraw $100

• T1.1: Fetch balance for T2.1: Fetch balance for

• Acct #12345: $500.00 Acct #12345: $500.00

• T2.2: Balance >= $100?

• T2.3: Yes, Bal = Bal - $100

• T2.4: Set DB balance to $400

• T2.5: End transaction

• T1.2: Bal = Bal + $100

• T1.3: Set DB balance to $600

• T1.4: End transaction

• The depositor might be pleased, but the bank won’t be!

Balance: $600

Balance: $400

Balance: $500

Time

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