Immortal DB: Transaction Time Support for SQL Server

Our {\em Immortal DB} prototype provides transaction time database support built into the Sql Server database engine, not layered on top. Transaction-time databases retain and provide access to all prior states of a database. Thus an update "inserts" a new {\em version} of a record while preserving the old version. Our prototype supports {\em as of} queries that return record versions of the database "as of" a specified time in the past. Immortal DB exploits three distinguishing technologies. (1)~Historical versions of a record are initially stored in the same disk page as the current version. (2)~Each version is lazily stamped with the clock time of its updating transaction after commit. (3)~Time-based page splits are used to accommodate arbitrarily large database histories and enable effective time-based indexing. We demonstrate the functionality of Immortal DB with a moving objects application that tracks cars in the Seattle area