Database concurrency control using data flow graphs

A specialized data flow graph, Database Flow Graph (DBFG) is introduced. DBFGs may be used for scheduling database operations, particularly in an MIMD database machine environment. A DBFG explicitly maintains intertransaction and intratransaction dependencies, and is constructed from the Transaction Flow Graphs (TFG) of active transactions. A TFG, in turn, is the generalization of a query tree used, for example, in DIRECT [15]. All DBFG schedules are serializable and deadlock free. Operations needed to create and maintain the DBFG structure as transactions are added or removed from the system are discussed. Simulation results show that DBFG scheduling performs as well as two-phase locking.