The Adaptive Server optimizer uses parallel query optimization strategies only when a given query is eligible for parallel execution. If the query is processed in parallel, showplan uses three separate messages to report:
The fact that some or all of the query was executed by the coordinating process and worker processes. The number of worker processes is included in this message.
The number of worker processes for each step of the query that is executed in parallel.
The degree of parallelism for each scan.
Note that the degree of parallelism used for a query step is not the same as the total number of worker processes used for the query.
For more examples of parallel query plans, see Chapter 7, “Parallel Query Optimization.”