compensation-log-record · shipping · also CLR

Compensation log record

An ARIES compensation log record describes a rollback action for redo and records where undo processing should continue.

CLRs are redo-only: recovery does not undo the compensation itself. PrevLSN follows the transaction's log chain; UndoNxtLSN bypasses already compensated work. A durable CLR can survive while the corresponding page update does not; redo restores that update before rollback continues. If the CLR was volatile and is lost, that progress is not preserved. These are original ARIES semantics, not a claim that every WAL engine uses CLRs. [1] [2] The companion's 12-state example is a single-page synthetic model, not a hardware crash test. [3]

Relations

related

write-ahead-log, log-sequence-number, page-lsn, fuzzy-checkpoint

Citations

1. Mohan, Haderle, Lindsay, Pirahesh and Schwarz. ARIES. ACM TODS 17(1), 1992, sections 3, 5.2 and 6.2-6.3. (accessed 2026-10-15)
2. C. Mohan. Repeating History Beyond ARIES. VLDB 1999, sections 3.2.1-3.2.2. (accessed 2026-10-15)
3. Hesela: ARIES rollback progress, with a synthetic executable trace (accessed 2026-10-15)

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