1. 检测数据库中的事件和等待
SELECT event, total_waits, total_timeouts,time_waited, average_wait
FROM v$system_event
2. 查询会话中的事件和等待时间
select sid, event, total_waits,average_wait
from v$session_event where sid=10;
3. 查询等待进程
SELECT sid, seq#, event, wait_time, state
FROM v$session_wait;
4. 监控全局区的性能
select * from v$sgastat;
5. 查询命中率
select gethitratio
from v$librarycache
where namespace = 'SQL AREA';
6. 当前 sql 语句
select sql_text, users_executing,
executions, loads
from v$sqlarea;
7. 查询高速缓存中的命中率
select sum(pins) "Executions", sum(reloads) "Cache Misses",
sum(reloads)/sum(pins)
from v$librarycache;
8. 查询全局字典中的有效装载次数
select namespace,pins,reloads,invalidations
from v$librarycache;
9. 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;
10. 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$filestat f, dba_data_files df
where f.file# = df.file_id
order by df.tablespace_name;
11. 监控文件系统的 I/O 比例
select substr(a.file#,1,2) "#", substr(a.name,1,30) "Name",
a.status, a.bytes, b.phyrds, b.phywrts
from v$datafile a, v$filestat b
where a.file# = b.file#;
12. 在某个用户下找所有的索引
select user_indexes.table_name, user_indexes.index_name,uniqueness, column_name
from user_ind_columns, user_indexes
where user_ind_columns.index_name = user_indexes.index_name
and user_ind_columns.table_name = user_indexes.table_name
order by user_indexes.table_type, user_indexes.table_name,
user_indexes.index_name, column_position;
13. 监控 SGA 中字典缓冲区的命中率
select parameter, gets,Getmisses , getmisses/(gets+getmisses)*100 "miss ratio",
(1-(sum(getmisses)/ (sum(gets)+sum(getmisses))))*100 "Hit ratio"
from v$rowcache
where gets+getmisses <>0
group by parameter, gets, getmisses;
14. 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;
15. 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;
16. 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$latch WHERE name IN ('redo allocation', 'redo copy');
17. 监控内存和硬盘的排序比率，最好使它小于 .10 ，增加 sort_area_size
SELECT name, value FROM v$sysstat WHERE name IN ('sorts (memory)', 'sorts (disk)');
18. 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
19. 找 ORACLE 字符集
select * from sys.props$ where name='NLS_CHARACTERSET';
20. 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
21. 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);
22. 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;
23 、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;