Incremental Hoarding and Reintegration in Mobile Environments

Disconnection is one of the popular techniques for operating in mobile environments and is here to stay, until long-range wireless connectivity becomes a reality. However, disconnection requires periodic hoarding and reintegration of data, which raises performance issues especially during weak connection. A common hoarding and reintegration mechanism involves complete transfer of contents. In order to hoard and reintegrate efficiently, an incremental approach is being introduced to do data transfers based on the delta between changes. Data objects are differentially transferred in either direction – to hoard from the server to the client, and to reintegrate changes made while disconnected from the client to the server – and are patched on the receiving side to generate full copies. QuickConnect and MoneyConnect are two important and useful features that are also being introduced to allow mobile users to control the amount of connection time and money spent during weakly connected re-integration. Performance evaluation of this system proves that it does efficient incremental hoarding and is beneficial on any type of connection. Analysis also shows that incremental reintegration is particularly beneficial in the weakly connected mode of operation. The incremental hoarding and reintegration setup is built within the Coda File System of the Carnegie Mellon University to replace the full file transfer mechanism with the incremental approach, based on the Revision Control System (RCS).