Design and Analysis of Integrated Concurrency-Coherence Controls

In a multi-system data sharing complex, the systems have direct access to all data. with sharing typically at the disk level. This necessitates global concurrency control and coherency control of local buffers in each system. We propose an integrated controller for handling both global concurrency and coherency control. and show that this leads to a si@fiint performance gain. ‘Ihe multi-system performance can be enhanced by use of an intermediate shared semiconductor memory. This gives rise 10 additional read-write synchronization and disk write serialization problems. We show these can be handled efficienlly by the integmted controller, while allowing for early transaction commit. Significant tnnsaction speedup and reduction in lock contention among transaclions are obtained. The decrease in lock contention allows the multiple systems 10 sustain a higher transaction throughput. A queueing model is used to quantify the performance bnproyement. Although intermediate memory can be employed as a buffering device our analysis shows that substantial performance gains can be realized when combined with the integrated concurrency-coherency controL