Performance of an OLTP application on Symmetry multiprocessor system

Sequent´s Symmetry series is a bus-based shared-memory multiprocessor. System performance in an OLTP (online transaction processing) relational database application was investigated using the TP1 benchmark. System performance was tested with fully cached benchmarks and with scaled benchmarks. In fully-cached tests, the entire database fits inside main memory. In scaled tests, the database is larger than available memory. In the fully-cached benchmark, performance was initially limited by bus saturation. The cause was the transfer of process context from processor to processor. This was eliminated by assigning each process to a processor. Processor affinity was combined with reductions in message passing within the database. Throughput was dramatically improved. The scaled tests were I/O bound. This bottleneck can be eliminated by connecting more disk drives or by increasing the main memory size