ORACLE常用操作

查询数据库当前进程的连接数：

select count(*) from v$process;

查看数据库当前会话的连接数:

select count(*) from v$session;

查看数据库的并发连接数：

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

查看当前数据库建立的会话情况：

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

查询数据库允许的最大连接数：　

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

或者：

show parameter processes;

修改数据库允许的最大连接数：(需要重启数据库才能实现连接数的修改)

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;

备注：UNIX 1个用户session对应一个操作系统process，而Windows体现在线程。

启动oracle

su - oracle
sqlplus system/pwd as sysdba   //进入sql
startup                                      //启动数据库
lsnrctl start                               //启动监听
sqlplus "/as sysdba"
shutdown immediate;
startup mount;
alter database open;

找到被锁的表：

SELECT dob.OBJECT_NAME Table_Name,
lo.SESSION_ID || ', ' || vss.SERIAL# 删除号,
lo.locked_mode,
lo.SESSION_ID,
vss.SERIAL#,
vss.action Action,
vss.osuser OSUSER,
vss.LOGON_TIME,
vss.process AP_PID,
VPS.SPID DB_PID,
vss.*
From v$locked_object lo, dba_objects dob, v$session vss, V$PROCESS VPS
Where lo.OBJECT_ID = dob.OBJECT_ID
and lo.SESSION_ID = vss.SID
AND VSS.paddr = VPS.addr
order by 2, 3, DOB.object_name

解锁：

ALTER system kill session '196, 1231'

数据库备份：

create table te.person_bak select * from te.person;
drop table te.person;
create table te.person as select * from te.person_bak@dblink_db;

创建序列

create sequence te.seq_pp_id

minvalue 1

maxvalue 9999999999999999999999999999

start with 5365

increment by 1

cache 20;

　　

–首先创建一个事务

declare

trans_id Varchar2(100);

begin

trans_id := dbms_transaction.local_transaction_id( TRUE );

end;

–查看事务隔离级别

SELECT s.sid, s.serial#,

　　CASE BITAND(t.flag, POWER(2, 28))

　　　　WHEN 0 THEN ‘READ COMMITTED’

　　　　ELSE ‘SERIALIZABLE’

　　END AS isolation_level

FROM vtransactiontJOINvtransactiontJOINvsession s ON t.addr = s.taddr AND s.sid = sys_context(‘USERENV’, ‘SID’);