Check for configuration parameters that perform automatic tuning.

For example, Oracle has a parameter called parallel_automatic_tuning.

Make sure intra-parallelism is enabled.

Intra-parallelism is the ability to run multiple threads on a single query. For example, on Oracle, look at parallel_adaptive_multi_user. On DB2, look at intra_parallel.

Verify the maximum number of parallel processes that are available for parallel executions.

For example, on Oracle, look at parallel_max_servers. On DB2, look at max_agents.

Verify the sizes for various resources used in parallelization.

For example, Oracle has parameters such as large_pool_size, shared_pool_size, hash_area_size, parallel_execution_message_size, and optimizer_percent_parallel. DB2 has configuration parameters such as dft_fetch_size, fcm_num_buffers, and sort_heap.

Verify the degrees of parallelism.

You may be able to set this option using a database configuration parameter or an option on the table or query. For example, Oracle has parameters parallel_threads_per_cpu and optimizer_percent_parallel. DB2 has configuration parameters such as dft_prefetch_size, dft_degree, and max_query_degree.

Turn off options that may affect database scalability.

For example, disable archive logging and timed statistics on Oracle.