1、查询当前系统中正在执行的sql:

SELECT osuser, username, sql_text from v$session a, v$sqltext b 
where a.sql_address =b.address order by address, piece;

2、查找死锁的语句:

SELECT l.session_id sid, s.serial#, l.locked_mode,l.oracle_username, 
l.os_user_name,s.machine, s.terminal, o.object_name, s.logon_time
FROM v$locked_object l, all_objects o, v$session s
WHERE l.object_id = o.object_id
AND l.session_id = s.sid
ORDER BY sid, s.serial#;

3、查看oracle的权限角色:

select * from dba_role_privs;    授予用户和其他角色的角色   
select * from dba_sys_privs;     授予用户和其他角色的系统权限   
select * from dba_tab_privs;     数据库中对象的所有授权
select * from user_role_privs;   查看当前用户的角色

4、oracle 查看已经执行过的sql 这些是存在共享池中的：

select * from v$sqlarea t order by t.LAST_ACTIVE_TIME desc;

5、【获取oracle前10条最耗资源的sql语句】：

SELECT * FROM 
  (
   SELECT PARSING_USER_ID
          EXECUTIONS,
          SORTS,
          COMMAND_TYPE,
          DISK_READS,
          sql_text
      FROM  v$sqlarea
     ORDER BY disk_reads DESC 
   )  
  WHERE ROWNUM<11;

--本篇文章转自：http://lvming1000.blog.163.com/blog/static/116860020140591752646/