To ensure the safest environment possible, Sybase strongly recommends that you install and invoke UDFs from a read-only IQ server node in a multiplex installation.
The 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 IQ server is stopped and restarted.
In environments where after-hours maintenance operations require a shutdown and restart of the IQ server, run some test queries after the Sybase IQ server has been restarted. This ensures that the appropriate libraries are loaded in memory for optimal query performance during business hours.