Value-added locking: concurrently supporting transactions and queries in DBMS

This paper presents an approach value-added locking (VAL), that allows effective transaction processing and the execution of complex, read-only, and long-lived queries simultaneously on the same database. VAL integrates the concepts of altruistic locking and quasi-copies to provide a mechanism that allows users, application designers to database administrators to fine-tune the system performance in terms of transaction throughput and queries´ average response times. By deploying VAL, a significant gain in system performance may be expected. It also shows that a conventional concurrency control mechanisms such as 2-phase locking becomes a special case of the approach