查詢當前數據庫連接數，進程數，啟動數據庫

查詢數據庫當前進程的連接數：

select count(*) from v$process;

查看數據庫當前會話的連接數：

elect count(*) from v$session;

查看數據庫的并發連接數：

select count(*) from v$session where status='ACTIVE';

查看當前數據庫建立的會話情況：

select sid,serial#,username,program,machine,status from v$session;

查詢數據庫允許的最大連接數：

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

或者：show parameter processes;

查詢所有數據庫的連接數

selectschemaname,count(*)fromv$sessiongroupbyschemaname;

查詢終端用戶使用數據庫的連接情況。

selectosuser,schemaname,count(*)fromv$sessiongroupbyschemaname,osuser;

#查看當前不為空的連接

select * from v$session where username is not null

#查看不同用戶的連接數

select username,count(username) from v$session where username is not null group by username

#連接數

select count(*) from v$session

#并發連接數

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

#最大連接

show parameter processes

#修改連接

alter system set processes = value scope = spfile

修改數據庫允許的最大連接數：

alter system set processes = 300 scope = spfile;

(需要重啟數據庫才能實現連接數的修改)

重啟數據庫：

shutdown immediate;

startup;

查看當前有哪些用戶正在使用數據：

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;

備注：UNIX 1個用戶session對應一個操作系統process，而Windows體現在線程。

oracle中查詢被鎖的表并釋放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

釋放session Sql:

alter system kill session 'sid, serial#'

alter system kill session '379, 21132'

alter system kill session '374, 6938'

查看占用系統io較大的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

找出耗cpu較多的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

查詢session被鎖的sql可以用一下語句

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;

啟動oracle

su - oracle

sqlplus system/pwd as sysdba //進入sql

startup //啟動數據庫

lsnrctl start //啟動監聽

sqlplus "/as sysdba"

shutdown immediate;

startup mount;

alter database open;

總結

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