Oracle学习之路【四】DBA常用语句

裘子惠

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--查看表锁
select * from sys.v_$sqlarea where disk_reads>100
--监控事例的等待
select event,sum(decode(wait_Time,0,0,1)) "Prev",
sum(decode(wait_Time,0,1,0)) "Curr",count(*) "Tot"
from v$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,
sum(nvl(a.bytes,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, 1, 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, gets, 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$librarycache
--监控 SGA 中重做日志缓存区的命中率，应该小于1%
SELECT name, gets, misses, immediate_gets, immediate_misses,
Decode(gets,0,0,misses/gets*100) ratio1,
Decode(immediate_gets+immediate_misses,0,0,
immediate_misses/(immediate_gets+immediate_misses)*100) ratio2
FROM v$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 .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_$sqlarea where executions>100
--查询使用CPU多的用户session
select a.sid,spid,status,substr(a.program,1,40) prog,a.terminal,osuser,value/60/100 value
from v$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.terminal,s.program
ORDER BY count(a.sid)

--表占用的空间
select   a.segment_name,sum(bytes)/1024/1024   from   user_segments   a
　　where   segment_type= 'TABLE'   
group   by   a.segment_name
　　
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