在Oracle中可以通过dba_hist_active_sess_history视图查看并发的会话，可以通过以下脚本查询出每个用户最大并发，当前的连接数，及profile限制的最大连接数等。

SELECT AA.USERNAME, AA.Max_s, AA.Min_s, AA.AG_s, BB.CNT, CC.LIMIT
  FROM (select username,
               max(curr_user) Max_s,
               min(curr_user) Min_s,
               round(avg(curr_user)) AG_s
          from (select username, snap_id, count(1) curr_user
                  from dba_hist_active_sess_history a, dba_users b
                 where --user_id = 65
                -- sample_time >= to_date('2014-06-27', 'yyyy-mm-dd')
                --and sample_time < to_date('2014-10-29', 'yyyy-mm-dd')
                ----and snap_id>=37306 and snap_id < 37401
                --snap_id>=36062 and snap_id < 38073   285240710
                 a.user_id = b.user_id
                 group by username, snap_id)
         group by username) AA,
       (SELECT USERNAME, COUNT(1) CNT FROM V$SESSION GROUP BY USERNAME) BB,
       (SELECT B.USERNAME, A.LIMIT
          FROM dba_profiles A, DBA_USERS B
         WHERE A.PROFILE = B.PROFILE
           and b.account_status = 'OPEN'
           AND A.resource_name = 'SESSIONS_PER_USER') CC
 WHERE AA.USERNAME = BB.USERNAME
   AND BB.USERNAME = CC.USERNAME;


结果如下：

USERNAME	MAX_S	MIN_S	AG_S	CNT	LIMIT
APP_user1	19	1	2	50	200
APP_user2	4	1	1	10	300
APP_user3	1	1	1	10	70
APP_user4	16	1	3	60	70
APP_user5	3	1	1	40	50
APP_user6	11	1	2	80	161
APP_user7	850	7	87	465	1000
APP_user8	11	1	2	80	90
APP_user9	7	1	2	17	80