oracle session

1.如何查看session级的等待事件？
当我们对数据库的性能进行调整时，一个最重要的参考指标就是系统等待事件。v$system_event,v$session_event,v$session_wait这三个视图里记录的就是系统级和session级的等待事件，通过查询这些视图你可以发现数据库的一些操作到底在等待什么？是磁盘I/O，缓冲区忙，还是插锁等等。
通过如下sql你可以查询你的每个应用程序到底在等待什么，从而针对这些信息对数据库的性能进行调整。

Select s.username,s.program,s.status,se.event,se.total_waits,se.total_timeouts,se.time_waited,se.average_wait
from v$session s, v$session_event se
Where s.sid=se.sid  And se.event not like 'SQl*Net%'  And s.status ='ACTIVE'  And s.username is not null

Select s.username,s.program,s.status,se.event,se.total_waits,se.total_timeouts,se.time_waited,se.average_wait
from v$session s, v$session_event se
Where s.sid=se.sid  And se.event not like 'SQl*Net%'  And s.status ='ACTIVE'  And s.username is not null

2.oracle中查询被锁的表并释放session

SELECT A.OWNER,A.OBJECT_NAME,B.XIDUSN,B.XIDSLOT,B.XIDSQN,B.SESSION_ID,B.ORACLE_USERNAME, B.OS_USER_NAME,B.PROCESS, B.LOCKED_MODE, C.MACHINE,C.STATUS,C.SERVER,C.SID,C.SERIAL#,C.PROGRAM
FROM ALL_OBJECTS A,V$LOCKED_OBJECT B,SYS.GV_$SESSION C
WHERE ( A.OBJECT_ID = B.OBJECT_ID ) AND (B.PROCESS = C.PROCESS ) ORDER BY 1,2

SELECT A.OWNER,A.OBJECT_NAME,B.XIDUSN,B.XIDSLOT,B.XIDSQN,B.SESSION_ID,B.ORACLE_USERNAME, B.OS_USER_NAME,B.PROCESS, B.LOCKED_MODE, C.MACHINE,C.STATUS,C.SERVER,C.SID,C.SERIAL#,C.PROGRAM
FROM ALL_OBJECTS A,V$LOCKED_OBJECT B,SYS.GV_$SESSION C
WHERE ( A.OBJECT_ID = B.OBJECT_ID ) AND (B.PROCESS = C.PROCESS ) ORDER BY 1,2

释放session Sql:

alter system kill session 'sid, serial#'
alter system kill session '379, 21132'
alter system kill session '374, 6938'

alter system kill session 'sid, serial#'
alter system kill session '379, 21132'
alter system kill session '374, 6938'

3.查看占用系统io较大的session

SELECT se.sid,se.serial#,pr.SPID,se.username,se.status,se.terminal,se.program,se.MODULE,se.sql_address,st.event,st.p1text,si.physical_reads,si.block_changes
FROM v$session se,　v$session_wait st,v$sess_io si,v$process pr
WHERE st.sid=se.sid 　AND st.sid=si.sid AND se.PADDR=pr.ADDR AND se.sid>6　AND st.wait_time=0 AND st.event NOT LIKE '%SQL%' ORDER BY physical_reads DESC

SELECT se.sid,se.serial#,pr.SPID,se.username,se.status,se.terminal,se.program,se.MODULE,se.sql_address,st.event,st.p1text,si.physical_reads,si.block_changes
FROM v$session se,　v$session_wait st,v$sess_io si,v$process pr
WHERE st.sid=se.sid 　AND st.sid=si.sid AND se.PADDR=pr.ADDR AND se.sid>6　AND st.wait_time=0 AND st.event NOT LIKE '%SQL%' ORDER BY physical_reads DESC

4.找出耗cpu较多的session

select a.sid,spid,status,substr(a.program,1,40) prog,a.terminal,osuser,value/60/100 value
    from v$session a,v$process b,v$sesstat c
    where c.statistic#=12 and c.sid=a.sid and a.paddr=b.addr order by value desc

select a.sid,spid,status,substr(a.program,1,40) prog,a.terminal,osuser,value/60/100 value
    from v$session a,v$process b,v$sesstat c
    where c.statistic#=12 and c.sid=a.sid and a.paddr=b.addr order by value desc

5.查询session被锁的sql可以用一下语句

select sys.v_$session.osuser,sys.v_$session.machine,v$lock.sid,
　　sys.v_$session.serial#,
　　decode(v$lock.type,
　　'MR', 'Media Recovery',
　　'RT','Redo Thread',
　　'UN','User Name',
　　'TX', 'Transaction',
　　'TM', 'DML',
　　'UL', 'PL/SQL User Lock',
　　'DX', 'Distributed Xaction',
　　'CF', 'Control File',
　　'IS', 'Instance State',
　　'FS', 'File Set',
　　'IR', 'Instance Recovery',
　　'ST', 'Disk Space Transaction',
　　'TS', 'Temp Segment',
　　'IV', 'Library Cache Invalida-tion',
　　'LS', 'Log Start or Switch',
　　'RW', 'Row Wait',
　　'SQ', 'Sequence Number',
　　'TE', 'Extend Table',
　　'TT', 'Temp Table',
　　'Unknown') LockType,
　　rtrim(object_type) || ' ' || rtrim(owner) || '.' || object_name object_name,
　　decode(lmode, 0, 'None',
　　1, 'Null',
　　2, 'Row-S',
　　3, 'Row-X',
　　4, 'Share',
　　5, 'S/Row-X',
　　6, 'Exclusive', 'Unknown') LockMode,
　　decode(request, 0, 'None',
　　1, 'Null',
　　2, 'Row-S',
　　3, 'Row-X',
　　4, 'Share',
　　5, 'S/Row-X',
　　6, 'Exclusive', 'Unknown') RequestMode,
　　ctime, block b
　　from v$lock, all_objects, sys.v_$session
　　where v$Lock.sid > 6
　　and sys.v_$session.sid = v$lock.sid
　　and v$lock.id1 = all_objects.object_id;