sa_unload_cost_model ( file_name )

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 hardware.

The sa_unload_cost_model system procedure allows you save a cost model to an ASCII file (file_name). You can then log into another database and use the sa_load_cost_model system procedure to load the cost model from the first database into the second one. This avoids having to recalibrate the second database.

Using the sa_unload_cost_model system procedure eliminates repetitive, time-consuming recalibration activities when there is a large number of similar hardware installations.

DBA authority

You must have write permissions where the file is created.

None

• ALTER DATABASE statement
• sa_load_cost_model system procedure
• Advanced: Query optimization

The following example unloads the cost model to a file called costmodel8:

CALL sa_unload_cost_model( 'costmodel8' );