Consider a transaction that updates each of the 100 employees' salaries in a table (there is one row per employee)under the immediate update mode and completes after a checkpoint but before a system failure.The system crashes after the checkpoint.What should the recovery procedure perform to make sure the transaction completes as desired?
A) Nothing
B) Redo forward from checkpoint
C) Undo
D) Undo followed by execution of the transaction again

Question

Quizplus · Accepted Answer

Under the immediate update mode, changes made by transactions are immediately written to disk. If a system crash occurs after a checkpoint, the recovery procedure should perform a redo operation starting from the checkpoint to ensure all changes made by transactions, including the salary updates, are correctly reflected in the database. This is because the checkpoint ensures that all transactions prior to it are completed and their effects are permanently recorded on disk. The redo operation will reapply all the actions of transactions that were in progress at the time of the checkpoint or started after it, ensuring the database is brought to a consistent state.

Consider a Transaction That Updates Each of the 100 Employees