I would like somebody helps me to undestand what does exactly "session invalidate" mean. TIA, p.t. I've tryied the DTML code example reported at the end, and I've got this result: The result: The 'data' name now refers to a new or existing session data object. data: id: 10360077861432189970, token: 54001646A0iEAi2X9io, contents: [] Developers can manually invalidate a session data object. When a session data object is invalidated, it will be flushed from the system, and will not be returned by subsequent references to REQUEST.SESSION or getSessionData(). The invalidate() method of a session data object causes this to happen: call invalidate And now, checking again for data session: The 'data' name now refers to an existing session data object or None if there was no existing browser id or session data object. data: id: 10360078530598187012, token: 54001646A0iEAi2X9io, contents: [] the DTML code: <pre> <dtml-let data="session_data_manager.getSessionData()"> The 'data' name now refers to a new or existing session data object. <b>data</b>: <dtml-var data> Developers can manually invalidate a session data object. When a session data object is invalidated, it will be flushed from the system, and will not be returned by subsequent references to REQUEST.SESSION or getSessionData(). The invalidate() method of a session data object causes this to happen: call invalidate <dtml-call "data.invalidate()"> </dtml-let> And now, checking again for data session: <dtml-let data="session_data_manager.getSessionData(create=0)"> The 'data' name now refers to an existing session data object or None if there was no existing browser id or session data object. <b>data</b>: <dtml-var data> </dtml-let> </pre>