监控数据库性能的"SQL"语句都有哪些？

来源：赛迪网    作者：罗丽娜

监控数据库性能的SQL语句：

1. 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;

2. 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;

3. 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;

4. 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#;

5.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;

6. 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;

7. 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;

 

8. 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;

9. 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;

10. 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');

11. 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)');

12. 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;

13. 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。

14. 找ORACLE字符集

select * from sys.props$ where name='NLS_CHARACTERSET';

15. 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

 

 

16. 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; 

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);

17. 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;

18、找使用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;