To meet these requirements in a layered architecture, we propose a multilevel transaction management utilizing layer-specific semantics. Based on the theoretical notion of multilevel serializability, a family of concurrency control strategies is developed. Suitable recovery protocols are investigated for aborting single transactions and for restarting the system after a crash. The choice of levels involved in a multilevel transaction strategy reveals an inherent trade-off between increased concurrency and growing recovery costs. A series of measurements has been performed in order to compare several strategies.
Preliminary results indicate considerable performance gains of the multilevel transaction approach.
The author's stated goal is to provide guidelines for the practical implementation of general multilevel transaction management schemes. The key schemes are described and developed in exhaustive detail. Sections include background and motivation, concurrency control, extensions addressing transaction abort management for multilevel transactions, crash recovery in such transactions, description of the prototype database used to validate the assertions, and preliminary results and conclusions from the experiments. The sections on background and motivation, prototype database description, and results and conclusions are excellent for readers at all levels. They are well written and illustrate a number of counterintuitive results.