Exploiting main memory DBMS features to improve real-time concurrency control protocols
Özgür Ulusoy, Alejandro Buchmann · ACM SIGMOD Record · 1996
this paper is joint work that resulted from this cooperation. Predictability of transaction execution is a basic issue in RTDBSs. Because of the unpredictability of page faults and the time required for I/O (3-4 orders of magnitude higher than memory accesses) the work on RTDBS concurrency control has made one of two possible assumptions: either the performance metric used is simply the percentage of transactions finishing their execution within their deadline, without giving any guarantees for an individual transaction, or the underlying database is memoryresident. Main memory databases become increasingly feasible due to the drastically falling memory prices and growing memory sizes. However, the concurrency control protocols developed so far for RTDBSs are derived from disk-resident DBMS concurrency control algorithms and do not exploit the inherent properties of main memory databases. An assumption underlying the recently published concurrency control protocols for RTDBSs is that predeclaration of locks is impractical because it is impossible to predict which instance of a relation will actually be accessed by a transaction. Therefore, the model of dynamic resource acquisition is assumed. Those protocols spend considerable CPU time for the detection and resolution of data conflicts and fine-grained lock management. This overhead reduces the effective CPU utilization, and leads to an increase in the number of missed transaction deadlines. It has been demonstrated that very large lock