The LHAM log-structured history data access method

Numerous applications such as stock market or medical information systems r equire that both historical and current data be logically integrated into a temporal database. The underlying access method must support different for ms of "time-travel" queries, the migration of old record versions onto inex pensive archive media, and high insertion and update rates. This paper pres ents an access method for transaction-time temporal data, called the log-st ructured history data access method (LHAM) that meets these demands. The ba sic principle of LHAM is to partition the data into successive components b ased on the timestamps of the record versions. Components are assigned to d ifferent levels of a storage hierarchy, and incoming data is continuously m igrated through the hierarchy. The paper discusses the LHAM concepts, inclu ding concurrency control and recovery, our full-fledged LHAM implementation , and experimental performance results based on this implementation. A deta iled comparison with the TSB-tree, both analytically and based on experimen ts with real implementations, shows that LHAM is highly superior in terms o f insert performance, while query performance is in almost all cases at lea st as good as for the TSB-tree; in many cases it is much better.