SQL/MX 2.x Reference Manual (H06.10+, J06.03+)

Metadata Tables
HP NonStop SQL/MX Reference Manual—544517-008
10-62
Query Optimization and Performance
NUMBER_OF_USERS Set to the number of users that can run concurrent
queries that use large amounts of memory. For
these queries, the optimizer uses this number to limit
the amount of memory available for one user. The
larger the number, the less memory available for
operators (such as hash join) that use much
memory.
Allowed values: 1 through 1,4294967295.
The default setting is 1, which means that all
available memory can be assigned to one query.
OLT_QUERY_OPT Set to ON or OFF. When set to ON, the NonStop
SQL/MX enables a fast path evaluation method for
certain simple SQL queries, such as a single table
unique select.
For additional information about this setting, see the
SQL/MX Query Guide.
The default is ON.
OPTIMIZATION_LEVEL Set to 0, 2, 3, or 5 to indicate increasing effort in
optimizing SQL queries. Values 1 and 4 are reserved
for future use.
For additional information about this setting, see the
SQL/MX Query Guide.
The default is 3.
OPTS_PUSH_DOWN_DAM Set to ON (1) or OFF (0). When set to ON, the
system considers pushing down a plan to DAM for
compound statements or nested joins. When set to
OFF, the system does not consider this option.
When pushing a plan down to DAM is possible (the
value is ON), NonStop SQL/MX might not select the
push-down plan because of its cost.
For additional information about this setting, see the
SQL/MX Query Guide.
The default is OFF.
PARALLEL_NUM_ESPS Set to the keyword SYSTEM or to the maximum
number of ESPs (an unsigned positive integer) that
should be used for a particular operator.
If set to SYSTEM, NonStop SQL/MX calculates the
value.
If set to a number, the value must be less than the
number of CPUs in the cluster.
For additional information about this setting, see the
SQL/MX Query Guide.
Allowable values: 1 through 2147483647.
The default is SYSTEM (no maximum).
Attribute Setting