ORACLE性能监控之监控SQL语句

 分析表 
analyze table tablename compute statistics for all indexes; 
analyze table tablename compute statistics for all indexed columns; 
analyze table tablename compute statistics for table; 

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; 

查看碎片程度高的表 

SELECT segment_name table_name , COUNT(*) extents 
FROM dba_segments WHERE owner NOT IN (SYS, SYSTEM) GROUP BY segment_name 
HAVING COUNT(*) = (SELECT MAX( COUNT(*) FROM dba_segments GROUP BY segment_name); 

表、索引的存储情况检查 

select segment_name,sum(bytes),count(*) ext_quan from dba_extents where 
tablespace_name=&tablespace_name and segment_type=TABLE group by tablespace_name,segment_name; 

select segment_name,count(*) from dba_extents where segment_type=INDEX and owner=&owner 
group by segment_name; 

找使用CPU多的用户session 

12是cpu used by this 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; 

监控表空间的 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; 


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; 

在某个用户下找所有的索引 

select user_indexes.table_name, user_indexes.index_name,uniqueness, column_name 
from user_ind_columns, user_indexes 
where user_ind_columns.index_name = user_indexes.index_name 
and user_ind_columns.table_name = user_indexes.table_name 
order by user_indexes.table_type, user_indexes.table_name, 
user_indexes.index_name, column_position; 


监控文件系统的 I/O 比例 

select substr(a.file#,1,2) "#", substr(a.name,1,30) "Name", 
a.status, a.bytes, b.phyrds, b.phywrts 
from v$datafile a, v$filestat b 
where a.file# = b.file#; 

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; 

select sum(pinhits-reloads)/sum(pins) "hit radio",sum(reloads)/sum(pins) "reload percent" 
from v$librarycache; 

监控 SGA 的命中率 

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); 

显示所有数据库对象的类别和大小 

select count(name) num_instances ,type ,sum(source_size) source_size , 
sum(parsed_size) parsed_size ,sum(code_size) code_size ,sum(error_size) error_size, 
sum(source_size) +sum(parsed_size) +sum(code_size) +sum(error_size) size_required 
from dba_object_size 
group by type order by 2; 

监控内存和硬盘的排序比率，最好使它小于 .10，增加 sort_area_size 

SELECT name, value FROM v$sysstat WHERE name IN (sorts (memory), sorts (disk)); 


监控当前数据库谁在运行什么SQL语句 

SELECT osuser, username, sql_text from v$session a, v$sqltext b 
where a.sql_address =b.address order by address, piece; 

监控字典缓冲区 

SELECT (SUM(PINS - RELOADS)) / SUM(PINS) "LIB CACHE" FROM V$LIBRARYCACHE; 
SELECT (SUM(GETS - GETMISSES - USAGE - FIXED)) / SUM(GETS) "ROW CACHE" FROM V$ROWCACHE; 
SELECT SUM(PINS) "EXECUTIONS", SUM(RELOADS) "CACHE MISSES WHILE EXECUTING" FROM V$LIBRARYCACHE; 

后者除以前者,此比率小于1％,接近0％为好。 

SELECT SUM(GETS) "DICTIONARY GETS",SUM(GETMISSES) "DICTIONARY CACHE GET MISSES" 
FROM V$ROWCACHE 

监控 MTS 

select busy/(busy+idle) "shared servers busy" from v$dispatcher; 

此值大于0.5时，参数需加大 

select sum(wait)/sum(totalq) "dispatcher waits" from v$queue where type=dispatcher; 
select count(*) from v$dispatcher; 
select servers_highwater from v$mts; 

servers_highwater接近mts_max_servers时，参数需加大 

碎片程度 

select tablespace_name,count(tablespace_name) from dba_free_space group by tablespace_name 
having count(tablespace_name)>10; 

alter tablespace name coalesce; 
alter table name deallocate unused; 

create or replace view ts_blocks_v as 
select tablespace_name,block_id,bytes,blocks,free space segment_name from dba_free_space 
union all 
select tablespace_name,block_id,bytes,blocks,segment_name from dba_extents; 

select * from ts_blocks_v; 

select tablespace_name,sum(bytes),max(bytes),count(block_id) from dba_free_space 
group by tablespace_name;

数据库性能监控的主要指标

                指标名                                       说明

SGA-system global area     数据库系统全局区的大小（Oracle中的SGA）。SGA存放的是数据库中所有用户的共同信息，SGA的大小会严重影响数据库的性能

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Logical I/O                         每秒逻辑读/写的次数。当我们向数据库做任何的操作时，Oracle都会先到SGA中查找下有没有我们所需要的数据，如有就即时返回，没有再通过Physical I/O来向data file读数据据，从而减少Physical I/O的读写

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Buffer cache Hit Ratio       共享池的命中率。这是衡量Logical I/O 的一个指标，如果命中率低，表明Physical I/O的 读写次数必然增多，数据库性能必然下降。一般命中率都在95%以上，低于这个比率说明缓存区的设置太小

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DBWR（N）                     数据库磁盘写进程的数目，当并发写多数据的时候，如果DBWR的数据不足以应付，DBWR写进程耗时必然多，容易产生等待时间或锁的时间

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Buffer  Cache                   数据共享区的大小。如果Buffer  Cache太小，会造成Physical I/O过多

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LGWR（N）                  重做日志文件写进程的数目，磁盘I/O过多是会严重影响数据库性能

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Redo Buffer Cache       重做日志缓存区的大小，这个缓存区的大小会影响到LGWR（N）的读/写次数