The power of the private workspace model

摘要

In the private workspace model of concurrency control the transaction management component of a database management system maintains a private workspace for each transaction. Data items accessed by a transaction, regardless of the access mode, are cached in the workspace. At transaction commit time, its updates are made permananet in the database. In this paper we want to focus our attention on the private workspace model as a framework for the design of concurrency control algorithms which do not require ww synchronization. We present a Two Phase Locking (2PL) derivative called Workspace 2PL (W2PL) and show that in a system employing W2PL no ww synchronization is needed and more importantly, no transaction will restart on a READ request. Furthermore, under the No Blind Writes assumption we can guarantee that no READ request will cause a transaction to starve, thus no Reader will be restarted or starved.