ReviewTHE COMFORT AUTOMATIC TUNING PROJECT

| This paper reports on results and experiences from the COMFORT automatic tuning project. The objective of the project has been to investigate architectural principles of self-tuning database and transaction processing systems, and to develop self-tuning methods for speciic performance tuning problems. A particular concern of the project has been to cope with workload dynamics and workload heterogeneity in multiuser systems. As a general guideline, an adaptive feedback control approach has been adopted, where observations of the current load characteristics are used to predict performance trends and to drive the dynamic adjustment of tuning parameters. As examples of these general principles, the paper discusses adaptive approaches to two speciic tuning problems and the developed solutions. First, we present a self-tuning load control method that copes with overload caused by excessive lock connicts that may occur during load surges. This connict-driven load control method adapts the multiprogramming level of the system to the evolving load characteristics dynamically and automatically. Secondly, we discuss the self-tuning LRU-K database buuering method, which makes intelligent buuering decisions by dynamically tracking the access frequency of pages, thus coping well with evolving access patterns. We discuss the rationale of these two self-tuning methods in great detail, and we present comprehensive performance evaluation experiments for both synthetic and trace-driven workloads.