A Log-Structured History Data Access Method (LHAM)

There are numerous applications that require on--line access to a history of business events. Ideally, both historical and current data should be logically integrated into some form of temporal database, also known as a multi-- version database, historical database, or rollback database. The underlying access method should support the migration of old record versions onto inexpensive write--once media, different forms of "time--travel" queries, and potentially high rates of update events. This paper introduces a new access method for history data, called the Log--structured History data Access Method (LHAM). The basic principle of LHAM is to partition the data into successive components based on the timestamps of the record versions, and to employ a rolling merge process for efficient data migration between components. The concept of a rolling merge process was introduced in [OCGO92] with the Log--Structured Merge Tree (LSM--tree). 1 Introduction There are numerous applications that ..