A method for ascertaining active sessions may include receiving a request to ascertain active sessions by a session information server; transmitting respective challenges for document contents, which indicate whether sessions are currently active, from the session information server to at least one document management server which has a respective associated communication session server, wherein in the case of precisely one document management server the latter has at least two associated session servers; receiving respective challenge responses from the document management server, which indicate active sessions controlled by the session server associated with the respective document management server or which indicate that such sessions currently do not exist, by the session information server; and transmitting a first response, which indicates one or more active sessions controlled by the session servers associated with the document management server or which indicates that such sessions currently do not exist, by the session information server.