unable to clear user session

Dear Experts ,

today we find one user is taking more memory in application server so that i try to clear user session from sm04 (logoff) but session is not responding for my request

in my investigation i found

sm51 -- no process is running by that user

ism66 is also th same

sm04 memory screen i found below details for that user

roll - 9562038

mem(tot) -2793755066

mem(priv) - 2968834696

and in terminal screen usage is showing 4GB

so please give me some ideas how can i clear that user from sm04 and login type is RFC and user is dialog user

Regards