1.查找耗时的sql：

select sql_text
from v$sql
where disk_reads > 1000 or (executions > 0 and buffer_gets/executions > 30000);

SELECT * FROM (
SELECT sql_text,buffer_gets,disk_reads FROM v$sql
ORDER BY buffer_gets,disk_reads DESC)
WHERE ROWNUM<=10;

2.其它重要sql语句　
        -- 逻辑读多的SQL
　　select * from (select buffer_gets, sql_text
　　from v$sqlarea
　　where buffer_gets > 500000
　　order by buffer_gets desc) where rownum<=30;
　　
　　-- 执行次数多的SQL
　　select sql_text,executions from
　　(select sql_text,executions from v$sqlarea order by executions desc)
　　where rownum<81;
　　
　　-- 读硬盘多的SQL
　　select sql_text,disk_reads from
　　(select sql_text,disk_reads from v$sqlarea order by disk_reads desc)
　　where rownum<21;
　　
　　-- 排序多的SQL
　　select sql_text,sorts from
　　(select sql_text,sorts from v$sqlarea order by sorts desc)
　　where rownum<21;
　　
　　--分析的次数太多，执行的次数太少，要用绑变量的方法来写sql
　　set pagesize 600;
　　set linesize 120;
　　select substr(sql_text,1,80) "sql", count(*), sum(executions) "totexecs"
　　from v$sqlarea
　　where executions < 5
　　group by substr(sql_text,1,80)
　　having count(*) > 30
　　order by 2;
　　
　　-- 游标的观察
　　set pages 300;
　　select sum(a.value), b.name
　　from v$sesstat a, v$statname b
　　where a.statistic# = b.statistic#
　　and b.name = 'opened cursors current'
　　group by b.name;
　　
　　select count(0) from v$open_cursor;
　　
　　select user_name,sql_text,count(0) from v$open_cursor
　　group by user_name,sql_text having count(0)>30;
　　
　　--查看当前用户&username执行的SQL
　　select sql_text from v$sqltext_with_newlines where (hash_value,address) in
　　(select sql_hash_value,sql_address from v$session where username='&username')
　　order by address,piece;