When a conversion service is requested to perform a conversion, it must first locate the correct conversion data within the z/OS Unicode environment. If the conversion data is not present, the service requests that the conversion data is "dynamically loaded" into the z/OS Unicode environment. (This is also known as "Unicode on demand.") When this happens, the service waits for the conversion to load, and then continues with the conversion. When the service is called again with the same type of conversion, it locates the conversion data within the z/OS Unicode environment and does not need to dynamically load anything.

It is recommended that most customers use dynamic loading to populate their z/OS Unicode environment.