redbookcover.gif (13955 bytes) Readings in Database Systems, 3rd Edition

Stonebraker & Hellerstein, eds.

Recovery: The REDO Phase

We repeat History to reconstruct state at crash:

Reapply all updates (even of aborted Xacts!), redo CLRs.

Scan forward from log rec containing smallest recLSN in D.P.T. For each CLR or update log rec LSN, REDO the action unless:

Affected page is not in the Dirty Page Table, or
Affected page is in D.P.T., but has recLSN > LSN, or
pageLSN (in DB) LSN.

To REDO an action:

Reapply logged action.
Set pageLSN to LSN. No additional logging!

Previous slide Next slide Back to first slide View graphic version

1998, Joseph M. Hellerstein.  Last modified 08/17/98.
Feedback welcomed.