Oracle Parallel Processing

Chapter 5. Monitoring and Tuning Parallel Execution

Parallel execution can significantly reduce the processing time required for queries and other SQL statements, but only if it is properly implemented and tuned. You must monitor and tune the performance of parallel execution in your environment on a regular basis. In this chapter you’ll learn about the various tools and procedures at your disposal for monitoring the parallel execution performance of a database. You’ll also find some tuning tips and information on some important Oracle8i enhancements related to parallel execution performance.

Tuning Overview

Oracle tuning in general is a very large area, but when you focus strictly on parallel execution, there are only a few tuning-related adjustments that you can make. These include:

• Changing the PARALLEL_MIN_SERVERS initialization parameter, which controls the minimum number of parallel slave processes maintained in the parallel slave process pool

• Changing the PARALLEL_MAX_SERVERS initialization parameter, which controls the maximum number of parallel slave processes maintained in the parallel slave process pool

• Changing the PARALLEL_SERVER_IDLE_TIME initialization parameter, which controls the amount of time a slave process is kept around when it’s not being used

• Changing the degree of parallelism, using the DEGREE and INSTANCES keywords, for either a statement or a table

• Changing your statements to avoid “parallel from serial” bottlenecks (i.e., those caused by your execution plan’s ...