Product:  DbVisualizer Pro 9.1.1

Build:  #2063 (2013/10/01 12:27)

Java VM:  Java HotSpot(TM) Client VM

Java Version:  1.7.0_40

Java Vendor:  Oracle Corporation

OS Name:  Windows 7

OS Arch:  x86

OS Version:  6.1

An error occurred while establishing the connection:

Long Message:

ORA-02391: exceeded simultaneous SESSIONS_PER_USER limit

Details:

   Type: java.sql.SQLException

   Error Code: 2391

   SQL State: 61000

1、查询用户连接数，连接方式（jdbc还是用户client），每个用户的连接数。

　　SELECT  username ,  COUNT(*),  machine FROM   v$session WHERE  username IS NOT NULL GROUP BY  username,  machine ORDER BY   username;

2、--当前的数据库连接数

  select count(*) from v$process ;

3、--数据库允许的最大连接数

select value from v$parameter where name = 'processes';

4、--修改最大连接数:

alter system set processes = 300 scope = spfile;

5、--查看当前有哪些用户正在使用数据

SELECT osuser, a.username,cpu_time/executions/1000000||'s', b.sql_text,machine from v$session a, v$sqlarea b where a.sql_address =b.address order by cpu_time/executions desc;

SELECT osuser, a.username,cpu_time/executions/1000000||'s', b.sql_text,machine from v$session a, v$sqlarea b where a.sql_address =b.address order by cpu_time/executions desc;

6.查询用户连接数，连接方式（jdbc还是用户client），每个用户的连接数。

select DISTINCT username ,count(*) from  v$session group by username order by username

7. 查看某个用户正在对数据库进行的操作。

 select *  from  v$session where username='username' and status='ACTIVE'