Disconnected Operation in the Thor Object-Oriented Database System

Abstract

This paper discusses issues raised by providing disconnected operation in the Thor object-oriented database system. Disconnected operation in such a system poses new challenges because of the small size of objects, the richness and complexity of their interconnections, the huge number of them, and the fact that they are accessed within atomic transactions. We propose three techniques to address these challenges: (1) using the database query language for hoarding; (2) using dependent commits to tentatively commit transactions at the disconnected client; (3) using the high-level semantic of objects to avoid transaction aborts.

Exo-Leasing: Escrow Synchronization for Mobile Clients of Commodity Storage Servers

“…A tentative transaction records intention to commit and allows the client to start up a next transaction. Tentative commits lead to dependent commits [9]: transaction T j depends on T i if it uses objects modified by T i because if T i ultimately aborts so must T j . A tentative commit that is not a dependent commit, defines an independent action: [5] a transaction T j that does not use objects modified by T i can commit even if T i aborts.…”