freeradius, user log in, simul use, and radius shut down

Hello What I have to do, when: user connect (simultaneous use 1) and while he is conncected to the network I shut down the radius. After that, when he reconnect he is not able to login to the network, so my question how I can clean sth in sql or what i have to run, to clear that dead sesions after what, the user will be able to connect to the network -- Z powazaniem Przemyslaw Backiel