|Topic:||Logical Logging to Extend Recovery to New Domains|
|Date:||Thursday, December 2, 1999|
|Place:||Gould-Simpson, Room 701|
Recovery can be extended to new domains at reduced logging cost by exploiting "logical" log operations. During recovery, a logical log operation may read data values from any recoverable object, not solely from values on the log or from the updated object. Hence, we needn't log these values, a substantial saving. We have developed a redo recovery theory that deals with general log operations and proved that the stable database remains recoverable when it is explained in terms of an installation graph. This graph was used to derive a write graph that determines a flush order for cached objects that ensures that the database remains recoverable.
Flush order introduces new complexity into cache management, including the need to atomically flush multiple cached objects. We show how the cache can be successfully managed even in the presence of this complexity. To illustrate the utility of this recovery work, we show how applications can be recovered with very low normal execution cost.