Abstract: Modern database systems provide media recovery by taking periodic backups and applying a transaction log to the backup to bring the data up-to-date. A multi-versioned database is one that retains and provides access to historical versions of data. The present invention shows how a history database, supported by the Time-Split B-tree, can be used to also provide the backup function of media recovery. Thus, the same versions used for database history are used for database backup. The cost of taking a backup is comparable to the cost of a good differential backup method, whereby only changed data is backed up. The media recovery cost, especially when the media failure is only partial, e.g., a single disk page, will frequently be lower.

Abstract: The present invention includes an approach to index tree structure changes which provides high concurrency while being usable with many recovery schemes and with many varieties of index trees. The present invention permits multiple concurrent structure changes. In addition, all update activity and structure change activity above the data level executes in short independent atomic actions which do not impede normal database activity. Only data node splitting executes in the context of a database transaction. This feature makes the approach usable with the diverse recovery mechanisms, while only impacting concurrency in a modest way. Even this impact can be avoided by re-packaging the atomic actions, at the cost of requiring more from the recovery system.