MODEC: A Multi-Granularity Mobile Object-Oriented Database Caching Mechanism, Prototype and Performance

An inherent limitation in mobile data access is due to the unreliable and low bandwidth wireless communication channel. Caching of useful database items from database server in local storage of mobile clients is effective in reducing data access latency and wireless bandwidth consumption. In the event of disconnection, cached data can also serve the purpose of partial query processing. In this paper, we present the implementation and evaluate a new caching mechanism for object-oriented database systems in a mobile environment called MODEC. MODEC possesses the capabilities of performing caching at multiple granularities and adapting to changes in data access pattern, providing improved performance through tolerating limited inconsistency to read-only transactions. This caching capabilities is supported via standard ODMG modeling constructs. The prototype of MODEC is implemented using ODE database. Empirical system performance results are obtained from experiments on the prototype with data from a real-life database. The results are validated against results obtained via detailed simulation studies on MODEC. Both sets of results are found to be consistent and are in favor of our MODEC mechanism in providing a feasible solution to the mobile data access problem under the constraints in a mobile environment.