Write-Ahead Logging (WAL)

• The Write-Ahead Logging Protocol:

  • Must force the log record for an update before the corresponding data page gets to disk.
  • Must write all log records for a Xact before commit.

• #1 guarantees Atomicity.

• #2 guarantees Durability.

• Exactly how is logging (and recovery!) done?

  • We’ll study the ARIES algorithms.

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