Database Recovery
Write-Ahead Logging (WAL)
Before any change to database, write to log first:
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Database Recovery
Learning Objectives
- •Understand write-ahead logging
- •Learn recovery techniques
Lesson Outline
LearnStep 1/2
Database Recovery
ARIES Recovery Algorithm
Three phases:
Checkpointing
Periodic snapshot to reduce recovery time:
Recovery Actions
| Transaction State | Action |
|---|---|
| Committed (in log) | Redo if needed |
| Uncommitted | Undo |