The optimizer uses cost models to determine optimal access plans for queries. The database server maintains a cost model for
each database. The cost model for a database can be recalibrated at any time using the CALIBRATE SERVER clause of the ALTER
DATABASE statement. For example, you might decide to recalibrate the cost model if you move the database onto non-standard
The sa_load_cost_model system procedure allows you to load a cost model that has been saved to file (file_name). Loading a cost model replaces the current cost model for the database.
The sa_unload_cost_model system procedure does not include CALIBRATE PARALLEL READ information in the file that sa_load_cost_model
Using the sa_load_cost_model system procedure can eliminate repetitive, time-consuming recalibration activities when there
is a large number of identical hardware installations.
Exclusive use of the database is required when loading the new cost model.
When loading a cost model, consider whether it was generated for a database that is located on similar hardware. Loading a
cost model from a database that is stored on significantly different hardware may cause poor performance due to inefficient