Formal specification, object oriented design, and implementation of an ephemeral logger for database systems

Recent attempts to relax the ACID rules of transaction processing in order to support Long-Lived Transactions (LLTs) have produced a number of systems which incorporate a meta-transactional framework to store the context of simple atomic transactions. Such a system creates problems for logger design, as a small number of very long transactions can fill the log leading to the premature termination of other transactions. Ephemeral Logging (EL) is a logging algorithm which performs generational garbage collection on the log, thus optimising disk space usage. Its claimed advantage over traditional loggers is most marked in a situation where there are a few long transactions amongst many short ones. This paper describes the formal specification of a transactional logger based on the EL algorithm, its modelling using Object-oriented design(OMT) and implementation. The application of the EL logger to new, emerging applications is also considered. At present the published performance data for this algorithm have been derived using a simulator. This report attempts to examine and scrutinise those results, and asks whether EL could be the logging method of choice in systems that support LLTs.