sql consuming high cpu

go to OEM grid
target
database
performance tab
top activity
Keep the cursor on the spike (there should be a major difference in the graph)
click on the SQL ID
get the SID.
use this command to get the serial# and the user
SQL> SELECT SID, SERIAL#, USERNAME FROM V$SESSION where SID='797';
kill the session (if the user requests)

If you want to go back far, you can click on top activity & choose historical and choose the date and time