What is the main purpose of taking a checkpoint in a log-based recovery system?
Correct answer B. To limit how much of the log must be scanned and replayed after a crash
Explanation
At a checkpoint the DBMS flushes modified buffers to disk and writes a checkpoint record. Changes made before that point are known to be on disk, so recovery can start redo from the checkpoint instead of the beginning of the log, which shortens restart time and lets old log space be reused. Checkpoints do not remove committed data, and modern ones need not lock all tables.
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