Q20

Consider the following log sequence of two transactions on a bank account, with initial balance $12000,$ that transfer $2000$ to a mortgage payment and then apply a $5\%$ interest. Suppose the database system crashes just before log record $7$ is written. When the system is restarted, which one statement is true of the recovery procedure? We must redo log record $6$ to set B to $10500$ We must undo log record $6$ to set B to $10000$ and then redo log records $2$ and $3$ We need not redo log records $2$ and $3$ because transaction T1 has committed We can apply redo and undo operations in arbitrary order because they are idempotent