The cord approach to Extensible Concurrency Control

Database management systems (DBMSs) have been increasingly used for advanced application domains, such as software development environments, network management, work ow management systems, computer-aided design and manufacturing, and managed healthcare. In these domains, the standard correctness model of serializability is often too restrictive. We introduce the notion of a Concurrency Control Language (CCL) that allows a database application designer to specify concurrency control policies to tailor the behavior of a transaction manager. A well-crafted set of policies de nes an extended transaction model. The necessary semantic information required by the CCL run-time engine is extracted from a task manager, a (logical) module by de nition included in all advanced applications. This module stores task models that encode the semantic information about the transactions submitted to the DBMS. We have designed a rulebased CCL, called cord, and have implemented a run-time engine that can be hooked to a conventional transaction manager to implement the sophisticated concurrency control required by advanced database applications. We present an architecture for systems based on cord and describe how we integrated the cord engine with the Exodus Storage Manager to implement Altruistic Locking. keywords: Extended Transaction Models, Extensible Concurrency Control, Transaction Manager Component, DBMS architecture c 1996, George T. Heineman and Gail E. Kaiser This paper is based on work sponsored in part by Advanced Research Project Agency order B128 monitored by Rome Lab F30602-94-C-0197, in part by National Science Foundation CCR-9301092, and in part by the New York State Science and Technology Foundation Center for Advanced Technology in High Performance Computing and Communications in Healthcare 94013. Heineman was also supported in part by an AT&T Fellowship. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the o cial policies, either expressed or implied, of the government, ARPA, NSF, NYSSTF, or AT&T.