Optimistic Data Replication for Mobile Applications

The number of mobile devices in use is exploding, and mobile devices are becoming more and more interconnected. As a result, users are demanding mobile access to their favorite applications as well as to new collaborative and group applications made possible by ad hoc networks of mobile clients. Many of these applications need to access data that is shared between multiple mobile clients. Optimistic data replication has emerged as the natural way to allow mobile clients with limited network connectivity to access global application data. In optimistic schemes, each machine keeps a cache of the data, and it reads and writes to this data without contacting other machines. Machines then communicate with each other to share their updates, resolving concurrent updates as needed. Optimistic replication has been used to manage data consistency among groups of well-connected servers, but the connectivity of devices in a mobile environment can often vary. In addition, mobile clients have a limited amount of memory, so solutions must ensure that cache sizes are kept to a minimum. In this paper, I will examine several existing systems that use optimistic data replication to support mobile applications. In my analysis, I will put an emphasis on the design decisions behind the system. These design decisions include the following general areas: