查询Oracle正在执行和执行过的SQL语句

---正在执行的
select a.username, a.sid,b.SQL_TEXT, b.SQL_FULLTEXT
  from v$session a, v$sqlarea b 
where a.sql_address = b.address 
---执行过的
select b.SQL_TEXT,b.FIRST_LOAD_TIME,b.SQL_FULLTEXT
  from v$sqlarea b
where b.FIRST_LOAD_TIME between '2009-10-15/09:24:47' and
       '2009-10-15/09:24:47' order by b.FIRST_LOAD_TIME 
（此方法好处可以查看某一时间段执行过的sql，并且 SQL_FULLTEXT 包含了完整的 sql 语句）

其他
select OSUSER,PROGRAM,USERNAME,SCHEMANAME,B.Cpu_Time,STATUS,B.SQL_TEXT 
from V$SESSION A LEFT JOIN V$SQL B ON A.SQL_ADDRESS=B.ADDRESS AND A.SQL_HASH_VALUE=B.HASH_VALUE order by b.cpu_time desc 

select address, sql_text, piece 
  from v$session, v$sqltext 
where address = sql_address 
  -- and machine = < you machine name > 
order by address, piece 

查找前十条性能差的sql. 
SELECT * FROM (select PARSING_USER_ID,EXECUTIONS,SORTS, 
COMMAND_TYPE,DISK_READS,sql_text FROM v$sqlarea 
order BY disk_reads DESC )where ROWNUM<10 ; 

查看占io较大的正在运行的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