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Redo Logging (cont)

Requirement for redo logging: write-ahead rule.

Data must be written to disk as follows:

  1. <START> transaction log record
  2. <UPDATE> log records indicating changes
  3. <COMMIT> log record
  4. the changed data elements themselves

Note that update log records now contain <T,X,v'>,
where v' is the new value for X.