–查找低效sql
SELECT EXECUTIONS,
DISK_READS,
BUFFER_GETS,
ROUND((BUFFER_GETS – DISK_READS) / BUFFER_GETS, 2) Hit_radio,
ROUND(DISK_READS / EXECUTIONS, 2) Reads_per_run,
SQL_TEXT
FROM V$SQLAREA
WHERE EXECUTIONS > 0
AND BUFFER_GETS > 0
AND (BUFFER_GETS – DISK_READS) / BUFFER_GETS < 0.8
ORDER BY 4 DESC;
–查找bad sql的方法：
select *
from (select buffer_gets, sql_text
from v$sqlarea
where buffer_gets > 500000
order by buffer_gets desc)
where rownum <= 30;
—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;