In order to improve performance, this object holds some information in RAM. When you call this method, the object will release all that data. It will reload that data whenever it needs it (using the ReadDataItem and ReadFormImage events.)

Normally, you will only want to call this method when you need to limit the amount of RAM consumed by your application. For the very best memory usage, you can call this method whenever you have finished processing a filled image. However, that may cause your system to run slowly as this object constantly reloads information that it discarded. A more balanced approach is to keep a list of a few most-recently-used FormModel objects. Whenever you replace an object in the list, you would call this method to release its memory.

Reference

FormModel Class
FormModel Members