If you are already using DDE to communicate with a TN3270 host, you may have some DDE transactions that accommodate your business needs. QWS3270 Secure has served as an application that DDE connects to in order to exchange data. A session connection with a host is required to issue DDE transaction commands. DDE is only useful for simple applications. The DDE connect command does not set up a session and it does not allow interactive command operation as HLLAPI does.