Summary, Cont.
 | Checkpointing: A quick way to limit the amount of log to scan on recovery.
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| Recovery works in 3 phases:
 | Analysis: Forward from checkpoint.
| Redo: Forward from oldest recLSN.
| Undo: Backward from end to first LSN of oldest Xact alive at crash.
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| Upon Undo, write CLRs.
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| Redo “repeats history”: Simplifies the logic!
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