调优帮助SQL

select count(*) from v$session  --连接数
Select count(*) from v$session where status='ACTIVE'　--并发连接数
alter system set processes = value scope = spfile;--重启数据库  修改连接
select value from v$parameter where value='processes'; --最大连接
alter system set processes= 300 scope=spfile;--修改连接数

shutdown immediate;
startup;
startup force;
select osuser,a.username,cup_time/executions/1000000||'s',sql_fulltext,machine from v$session a,v$sqlarea b where a.sql_address=b.address order by cup_time/executions desc;

SELECT osuser, username, sql_text from v$session a, v$sqltext b
where a.sql_address =b.address order by address, piece;--当前运行语句

SELECT SQL_TEXT FROM V$SQL--运行过

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;
--Cpu多

sqlplus / as sysdba alter user sys identified by

创建表空间
create tablespace platform. datafile 'e:\oracle\product\10.1.0\oradata\orcl\platform.dbf' size 1024M;

SQL> alter tablespace platform. add datafile 'e:\oracle\product\10.1.0\oradata\or
cl\platform1.dbf' size 4096m;

SELECT TO_NUMBER(TO_DATE('2005-03-29 12:30:45', 'YYYY-MM-DD HH24:MI:SS') - TO_DATE('1970-01-01 8:0:0', 'YYYY-MM-DD HH24:MI:SS')) * 24 * 60 * 60 * 1000 FROM DUAL;

清理回收站
coon as sysdba
purge DBA_RECYCLEBIN
查看回收站
show recyclebin
还原回收站
flashback table emp to before drop ;
1、从回收站恢复时重命名表

SQL> flashback table t2 to before drop rename to t4 ;

2、删除回收站指定的表

SQL> purge table t4;

3、清空回收站

SQL> purge recyclebin

4、删除表时不经过回收站直接删除

SQL> drop table t3 purge ;