--查找bad sql的方法:
　　select * from (select buffer_gets, sql_text
　　from v$sqlarea
　　where buffer_gets >500000
　　order by buffer_gets desc) where rownum<=30;

　　--執行次數SQL

　　select sql_text,executions from
　　(select sql_text,executions from v$sqlarea order by executions desc)
　　where rownum<81;

　　--讀磁盤多的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;

　　--分析次數太多，執行次數太少，要用綁定綁定變量寫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;

　　--遊標的觀察

　　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;

--查看當前用戶執行的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;