Page History

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WAL file segments and rotation structure

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See also WAL history size section below

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If we observe only CP begin and there is no CP end marker that means CP not finished; we have not consistent page store.

For crash without CP running restore is simple, logical record are applied.

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Let’s suppose we crash occurred at the middle of checkpoint. In that case restore process will discover markers for CP1 and 2 start and CP 1 end.

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For completed checkpoint CP1 we apply only physical records, for incomplete CP2  - only logical (as physical may be corrupted).

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