SELECT VS.SID, VS.USERNAME, VS.OSUSER, VS.PROCESS FG_PID, VP.SPID BG_PID FROM V$SESSION VS, V$PROCESS VP WHERE VS.PADDR = VP.ADDR;

SID  USERNAME        OSUSER     FG_PID    BG_PID
---- --------------- ---------- --------- ---------
14   QZBHS1          QZBHS1     2924:3744 1948
29   QZBHS1          QZBHS1     3632:3844 15452
51   QZBHS1          QZBHS1     4644:3892 5438

Issued in unix (as the oracle unix user, the user thats owns the database) :

kill -9 1948
kill -9 15452
kill -9 5438