--查看表锁
select * from sys.v_$sqlarea where disk_reads > 100;

--监控事例的等待
select event,
sum(decode(wait_Time,1)) "Prev",1,0)) "Curr",
count(*) "Tot"
from v$session_Wait
group by event
order by 4;

--回滚段的争用情况
select name,waits,gets,waits / gets "Ratio"
from v$rollstat a,v$rollname b
where a.usn = b.usn;

--查看前台正在发出的sql语句
select user_name,sql_text 　　
from v$open_cursor 　　
where sid in (select sid
from (select sid,serial#,username,program 　　
from v$session 　　
where status = 'ACTIVE'));

--数据表占用空间大小情况
select segment_name,tablespace_name,bytes,blocks
from user_segments
where segment_type = 'TABLE'
ORDER BY bytes DESC,blocks DESC;

--查看表空间碎片大小
select tablespace_name,
round(sqrt(max(blocks) / sum(blocks)) *
(100 / sqrt(sqrt(count(blocks)))),
2) FSFI
from dba_free_space
group by tablespace_name
order by 1;

--查看表空间占用磁盘情况
select b.file_id 文件ID号,
b.tablespace_name 表空间名,
b.bytes 字节数,
(b.bytes - sum(nvl(a.bytes,0))) 已使用,
sum(nvl(a.bytes,0)) 剩余空间,0)) / (b.bytes) * 100 剩余百分比
from dba_free_space a,dba_data_files b
where a.file_id = b.file_id
group by b.tablespace_name,b.file_id,b.bytes
order by b.file_id;

--查看session使用回滚段
SELECT r.name 回滚段名,
s.sid,
s.serial#,
s.username 用户名,
t.status,
t.cr_get,
t.phy_io,
t.used_ublk,
t.noundo,
substr(s.program,78) 操作程序
FROM sys.v_$session s,sys.v_$transaction t,sys.v_$rollname r
WHERE t.addr = s.taddr
and t.xidusn = r.usn
ORDER BY t.cr_get,t.phy_io;

--查看SGA区剩余可用内存
select name,
　　　　　　sgasize / 1024 / 1024　　　　　　　　"Allocated(M)",
　　　　　　bytes / 1024　　　　　　　　　　　"自由空间(K)",
　　　　　　round(bytes / sgasize * 100,2) 　　　"自由空间百分比(%)" 　　
from (select sum(bytes) sgasize from sys.v_$sgastat) s,
sys.v_$sgastat f 　　
where f.name = 'free memory';

--监控表空间I/O比例
select df.tablespace_name name,
df.file_name "file",
f.phyrds pyr,
f.phyblkrd pbr,
f.phywrts pyw,
f.phyblkwrt pbw
from v$filestat f,dba_data_files df
where f.file# = df.file_id
order by df.tablespace_name;

--监控SGA命中率
select a.value + b.value "logical_reads",
c.value "phys_reads",
round(100 * ((a.value + b.value) - c.value) / (a.value + b.value)) "BUFFER HIT RATIO"
from v$sysstat a,v$sysstat b,v$sysstat c
where a.statistic# = 38
and b.statistic# = 39
and c.statistic# = 40;

--监控 SGA 中字典缓冲区的命中率
select parameter,
gets,
Getmisses,
getmisses / (gets + getmisses) * 100 "miss ratio",
(1 - (sum(getmisses) / (sum(gets) + sum(getmisses)))) * 100 "Hit ratio"
from v$rowcache
where gets + getmisses <> 0
group by parameter,getmisses;

--监控 SGA 中共享缓存区的命中率，应该小于1%
select sum(pins) "Total Pins",
sum(reloads) "Total Reloads",
sum(reloads) / sum(pins) * 100 libcache
from v$librarycache;

--监控 SGA 中重做日志缓存区的命中率，应该小于1%
SELECT name,
misses,
immediate_gets,
immediate_misses,
Decode(gets,misses / gets * 100) ratio1,
Decode(immediate_gets + immediate_misses,
0,
immediate_misses / (immediate_gets + immediate_misses) * 100) ratio2
FROM v$latch
WHERE name IN ('redo allocation','redo copy');

--监控内存和硬盘的排序比率，最好使它小于 0.10
SELECT name,value
FROM v$sysstat
WHERE name IN ('sorts (memory)','sorts (disk)');

--监控字典缓冲区
SELECT SUM(GETS) "DICTIONARY GETS",
SUM(GETMISSES) "DICTIONARY CACHE GET MISSES"
FROM V$ROWCACHE;

--非系统用户建在SYSTEM表空间中的表
SELECT owner,table_name
FROM DBA_TABLES
WHERE tablespace_name in ('SYSTEM','USER_DATA')
AND owner NOT IN
('SYSTEM','SYS','OUTLN','ORDSYS','MDSYS','SCOTT','HOSTEAC');

--性能最差的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 < 100;

--读磁盘数超100次的sql
select * from sys.v_$sqlarea where disk_reads > 100;

--最频繁执行的sql
select * from sys.v_$sqlarea where executions > 100;

--查询使用cpu多的用户session
select a.sid,
spid,
status,
substr(a.program,40) prog,
a.terminal,
osuser,
value / 60 / 100 value
from v$session a,v$process b,v$sesstat c
where c.statistic# = 12
and c.sid = a.sid
and a.paddr = b.addr
order by value desc;

--当前每个会话使用的对象数 SELECT a.sid,s.terminal,s.program,count(a.sid) FROM V$ACCESS a,V$SESSION s WHERE a.owner <> 'SYS' AND s.sid = a.sid GROUP BY a.sid,s.program ORDER BY count(a.sid);