SQL/MX 2.x Query Guide (G06.24+, H06.03+)

Parallelism
HP NonStop SQL/MX Query Guide—523728-003
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System Default Settings That Affect Parallelism
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PARALLEL_NUM_ESPS
Maximum number of ESPs an operator can use (for fewer CPUs per operator).
Limits the maximum number of ESPs per operator to a value less than the number
of CPUs in the cluster. Limits the number but does not choose which CPUs to use.
The system-defined default setting is the number of processors in the cluster.
If this attribute is not set by the user (SYSTEM setting), the optimizer calculates the
degree of parallelism. The optimizer chooses a degree of parallelism equal to the
number of CPUs in the cluster times the number of ESPs per CPU. By default, the
number of ESPs per CPU is one (1), so typically the optimizer chooses the degree
of parallelism equal to the number of CPUs in the cluster.
If a value is specified for the PARALLEL_NUM_ESPS attribute, the optimizer uses
that value for the degree of parallelism unless the value exceeds the number of
CPUs in the cluster, in which case it uses the number of CPUs in the cluster as the
degree of parallelism. Allowable settings are any unsigned positive integer or
SYSTEM.
The REMOTE_ESP_ALLOCATION attribute also affects parallelism. For more
information, see REMOTE_ESP_ALLOCATION on page 4-12.