The Session Database is used to hold information about current sessions as part of Simultaneous-Use limit checking. It can also be used by external utilities for querying the on-line user population. If you do not specify a SessionDatabase clause in your configuration file, the database will be kept internal to radiusd, which is faster, but cannot be used to synchronise multiple instances of Radiator.

If you want to enforce Simultaneous-Use limits and you are running multiple instances of Radiator, you must specify an external Session Database for each Radiator, and you must ensure that all instances of Radiator use the same Session Database. If you fail to do this, Radiator will not be able to correctly enforce Simultaneous-Use limits, and may allow people to log in who have already exceeded their limit.