Undo vs. Redo
Undo drawbacks
- Have to write changes before commit.
- Random writes: expensive
Redo drawbacks
- Have to write only log changes before commit.
- Don't let uncommitted changes to be written to disk.
- Faster I/O, but high memory requirements.
Undo/Redo logging
- Best of both worlds.
- Quite complex.
ARIES papers.
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