SPD Server includes
more advanced methods to optimize WHERE clauses. Before SPD Server
4.0, the rule-based, heuristic WHERE clause planner WHINIT was used
to manually tune queries for performance. SPD Server provides dynamic
WHERE clause costing, an automatic feature that can replace the need
to manually tune queries. SPD Server dynamic WHERE-costing uses factors
of duplicity and distribution to calculate relative processor costs
of various WHERE clause options. SPD Server users can use server
parameter commands in the
spdsserv.parm file
or macro variables to turn dynamic WHERE-costing on and off. If dynamic
WHERE-costing is turned off, SPD Server reverts to using the rules-based
WHERE clause planner.