数据库监控

数据库监控

--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)