The sent messages are not stored on the modem and the received messages are removed after they are read in by Diafaan SMS Server. However, you probably want to prevent logging of sent and received messages.
It is not possible to turn off logging in Diafaan SMS Server but you can limit logging to as little as one day. Just select the menu options Actions-Options-Logging and set Remove log items and events to one day.
Regards,
Henk