Real-Time Client-Server Push Strategies: Specification and Evaluation

The widespread use of networked environments and the recent availabilityof high network bandwidthshas rekindled interest in the area of automatic data refresh/update mechanisms. In many application areas, the updated information has a limited period of usefulness. Therefore, the development of systems and protocols that can handle such update tasks within predefined deadlines is required. In this paper, we propose and evaluate two real-time update-propagation mechanisms in a client-server environment. The main idea is the transport of update transactions to the location of the cached data rather than the updated data itself. Unlike current push mechanisms, the propagation of update transactions to client sites is neither periodic nor mandatory. Instead, it is based on client-specific criteria which depend on the contents of the database object being updated. We examine real-time push scheduling issues using the popular client-server database model as our underlying framework and carry out a performance scalabilitystudy under varying system configurations.