Distributed version management for read-only actions (extended abstract)

Abstract

Typical concurrency control protocols for atomic actions, such as two-phase locking, perform poorly for long read-only actions. We present three new concurrency control protocols that eliminate all interference between read-only actions and update .actions, and thus offer significantly improved performance for read-only actions. The protocols work by maintaining multiple versions of the system state; read-only actions read old versions, while update actions manipulate the most recent version. We focus on the problem of managing the storage required for old versions in a distributed system. One of the protocols uses relatively little space, but has a potentially significant communication cost. The other protocols use more space, but may be cheaper in terms of communication.