Initially Executing a User-Defined Function

To ensure the safest environment possible, install and invoke UDFs from a read-only server node in a multiplex installation.

The SAP Sybase IQ server does not load the library containing the UDF code until the first time the UDF is invoked. The first execution of a UDF residing in a library that has not yet been loaded may be unusually slow. After the library is loaded, the subsequent invocation of the same UDF or another UDF contained in the same library have the expected performance.

• Libraries using the stored procedure SA_EXTERNAL_LIBRARY_UNLOAD – These libraries are not reloaded when the SAP Sybase IQ server is stopped and restarted.

In environments where after-hours maintenance operations require a shutdown and restart of the server, run some test queries after the server has been restarted. This ensures that the appropriate libraries are loaded in memory for optimal query performance during business hours.

• Managing External Libraries
  Each external library is loaded the first time a UDF that requires it is invoked. A loaded library remains loaded for the life of the server. It is not loaded when a CREATE FUNCTION or CREATE PROCEDURE call is made, nor is it automatically unloaded when a DROP FUNCTION or DROP PROCEDURE call is made.