查看oracle数据库的连接数以及用户

----跟踪session中锁表
SELECT s.username, l.type,
decode(l.type,'TM','TABLE LOCK',
'TX','ROW LOCK',
NULL) LOCK_LEVEL,
o.owner,o.object_name,o.object_type,
s.sid,s.serial#,s.terminal,s.machine,s.program,s.osuser,s.status
FROM v$session s,v$lock l,dba_objects o
WHERE l.sid = s.sid
AND l.id1 = o.object_id(+)
AND s.username is NOT NULL
and s.username = 'NC633'
and decode(l.type,'TM','TABLE LOCK',
'TX','ROW LOCK',
NULL) is not null
order by l.type;

select count(*) from v$session;--查询oracle的连接数
select count(*) from v$session where status='ACTIVE';--查询oracle的并发连接数

select username,count(username) from v$session where username is not null group by username;--查看不同用户的连接数

select * from all_users;--查看所有用户：

--查看用户或角色系统权限(直接赋值给用户或角色的系统权限)：
select * from dba_sys_privs;
select * from user_sys_privs;

--查看角色(只能查看登陆用户拥有的角色)所包含的权限
select * from role_sys_privs;
--查看用户对象权限：
select * from dba_tab_privs;
select * from all_tab_privs;
select * from user_tab_privs;
--查看所有角色：
select * from dba_roles;
--查看用户或角色所拥有的角色：
select * from dba_role_privs;
select * from user_role_privs;
--查看哪些用户有sysdba或sysoper系统权限(查询时需要相应权限)
select * from V$PWFILE_USERS;

select count(*) from v$process --当前的连接数
select value from v$parameter where name = 'processes' --数据库允许的最大连接数

修改最大连接数:
alter system set processes = 300 scope = spfile;

重启数据库:
shutdown immediate;
startup;

--查看当前有哪些用户正在使用数据
SELECT osuser, a.username,cpu_time/executions/1000000||'s', sql_fulltext,machine
from v$session a, v$sqlarea b
where a.sql_address =b.address order by cpu_time/executions desc;
select count(*) from v$session #连接数

select count(*) from v$session where status='ACTIVE'　#并发连接数

show parameter processes #最大连接

alter system set processes = value scope = spfile;重启数据库 #修改连接

SQL> Select count(*) from v$session where status='ACTIVE' ;

COUNT(*)
----------
20

SQL> Select count(*) from v$session;

COUNT(*)
----------
187

SQL> show parameter processes;

NAME TYPE VALUE
------------------------------------ ----------- ----------
aq_tm_processes integer 0
db_writer_processes integer 1
gcs_server_processes integer 0
job_queue_processes integer 10
log_archive_max_processes integer 2
processes integer 450
SQL>

并发指active,I SEE

SQL> select count(*) from v$session #连接数
SQL> Select count(*) from v$session where status='ACTIVE'　#并发连接数
SQL> show parameter processes #最大连接
SQL> alter system set processes = value scope = spfile;重启数据库 #修改连接

unix 1个用户session 对应一个操作系统 process
而 windows体现在线程

DBA要定时对数据库的连接情况进行检查，看与数据库建立的会话数目是不是正常，如果建立了过多的连接，会消耗数据库的资源。同时，对一些“挂死”的连接，可能会需要DBA手工进行清理。
以下的SQL语句列出当前数据库建立的会话情况:
select sid,serial#,username,program,machine,status
from v$session;
输出结果为:
SID SERIAL# USERNAME PROGRAM MACHINE STATUS
---- ------- ---------- ----------- --------------- --------
1 1 ORACLE.EXE WORK3 ACTIVE
2 1 ORACLE.EXE WORK3 ACTIVE
3 1 ORACLE.EXE WORK3 ACTIVE
4 1 ORACLE.EXE WORK3 ACTIVE
5 3 ORACLE.EXE WORK3 ACTIVE
6 1 ORACLE.EXE WORK3 ACTIVE
7 1 ORACLE.EXE WORK3 ACTIVE
8 27 SYS SQLPLUS.EXE WORKGROUP\\WORK3 ACTIVE
11 5 DBSNMP dbsnmp.exe WORKGROUP\\WORK3 INACTIVE
其中，
SID 会话(session)的ID号;
SERIAL# 会话的序列号，和SID一起用来唯一标识一个会话;
USERNAME 建立该会话的用户名;
PROGRAM 这个会话是用什么工具连接到数据库的;
STATUS 当前这个会话的状态，ACTIVE表示会话正在执行某些任务，INACTIVE表示当前会话没有执行任何操作;
如果DBA要手工断开某个会话，则执行:
alter system kill session \'SID,SERIAL#\'

sql语句SQL语句如下：

SELECT username, machine, program, status, COUNT (machine) AS
连接数量
FROM v$session
GROUP BY username, machine, program, status
ORDER BY machine;

显示结果（每个人的机器上会不同）

SCHNEIDER|WORKGROUD\WANGZHENG|TOAD.exe|ACTIVE|1
SCHNEIDER|WORKGROUP\597728AA514F49D|sqlplusw.exe|INACTIVE|1
|WWW-Q6ZMR2OIU9V|ORACLE.EXE|ACTIVE|8
PUBLIC|||INACTIVE|0 按主机名查询SELECT COUNT(*) FROM V$SESSION WHERE MACHINE = 'DXMH'; 'DXMH'为主机名 数据恢复语句 create table informationlaw_bak
as
select * from informationlaw as of TIMESTAMP to_timestamp('20121126 103435','yyyymmdd hh24miss'); //按机器名分组查select username,machine,count(username) from v$session where username is not null group by username,machine;