7. Stage 5--Run a Multi-user Concurrency Test : Small Data Volumes
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Small Data Volumes
We have observed that some queries that operate on relatively small data volumes do not need to be executed in parallel to still run quickly. Queries processing even a few thousand rows can run well on just one or two cores, and actually run slower when given more cores, due to the inter-process communication overheads incurred.
So if your queries process only a small number of rows, consider making the max_parallelism_level settings very low from the outset if you are targeting large numbers of concurrent users.