Timestamp ordering concurrency control mechanisms for transactions of various length

Timestamp ordering concurrency control mechanisms were considered to be quite suitable for distributed database systems, since transactions to be rolled badk can be determined locally at each site. Experiments, however, have shown that timestamp ordering mechanisms do not seem to be efficient and has a starvation problem for long transactions. In this paper, to improve efficiency of timestamp ordering mechanisms we propose to use a termination timestamp which is defined by a predicted commitment time or a predicted last read/write request time of a transaction. Besides other advantages the mechanism simplifies operations required for abort selection. The abort selection method introduced by the authors tries to improve the efficienty by selecting a proper transaction to be rolled back when conflict occurs. Comparison of several timestamp ordering methods obtained by combining these techniques is also given.