Show top 25 SQL Statements, sorted per CPU usage:
SELECT * FROM (SELECT s.username, s.machine, s.terminal, a.sql_id, a.cpu_time/1000000 cpu_time, a.elapsed_time/1000000 elapsed_time, a.disk_reads, a.buffer_gets, a.rows_processed , a.sql_text FROM v$sqlarea a, v$session s WHERE a.sql_id = s.sql_id ORDER BY a.cpu_time DESC ) WHERE rownum <=25;
Perhaps MOATS is more efficient.
Mumbai is also a nice performance monitoring toolset.