Reference Work Entry

Encyclopedia of Database Systems

pp 517-522

Crash Recovery

  • Theo HärderAffiliated withUniversity of Kaiserslautern


Failure handling; System recovery; Media recovery; Online recovery; Restart processing; Backward recovery


In contrast to transaction aborts, a crash is typically a major failure by which the state of the current database is lost or parts of storage media are unrecoverable (destroyed). Based on log data from a stable log, also called temporary log file, and the inconsistent and/or outdated state of the permanent database, system recovery has to reconstruct the most recent transaction-consistent database state. Because DBMS restart may take too long to be masked for the user, a denial of service can be observed. Recovery from media failures relies on the availability of (several) backup or archive copies of earlier DB states – organized according to the generation principle – and archive logs (often duplexed) covering the processing intervals from the points of time the backup copies were created. Archive recovery usually causes much longer outages than ...

This is an excerpt from the content