Chapter 25: Parallel Query Optimization

This chapter describes the basic strategies that Adaptive Server uses to perform parallel queries and explains how the optimizer applies those strategies to different queries. Parallel query optimization is an automatic process, and the optimized query plans created by Adaptive Server generally yield the best response time for a particular query.

However, knowing the internal workings of a parallel query can help you understand why queries are sometimes executed in serial, or with fewer worker processes than you expect. Knowing why these events occur can help you make changes elsewhere in your system to ensure that certain queries are executed in parallel and with the desired number of processes.