查看数据库性能 常用SQL

---内存评估

--缓冲区命中率

select (1 - (sum(decode(name, 'physical reads', value, 0)) /

(sum(decode(name, 'db block gets', value, 0)) +

sum(decode(name, 'consistent gets', value, 0))))) * 100 "Hit Ration"

from v$sysstat;

--数据字典命中率

select (1 - (sum(getmisses) / sum(gets))) * 100 "Hit Ration"

from v$rowcache;

--库缓存命中率

select sum(pins) / (sum(pins) + sum(reloads)) * 100 "Hit Ratio"

from v$librarycache;

--内存中的排序

select a.value "Dish Sorts",

b.value "Memor Sorts",

round((100 * b.value) /

decode((a.value + b.value), 0, 1, (a.value + b.value)),

2) "Pct Memory Sorts"

from v$sysstat a, v$sysstat b

where a.name = 'sorts (disk)'

and b.name = 'sorts (memory)';

--空闲的数据缓冲区比例

select decode(state,

0,

'FREE',

1,

decode(lrba_seq, 0, 'AVAILABLE', 'BEING USED'),

3,

'BEING USED',

state) "Block Status",

count(*)

from x$bh

group by decode(state,

0,

'FREE',

1,

decode(lrba_seq, 0, 'AVAILABLE', 'BEING USED'),

3,

'BEING USED',

state);

--最浪费内存的前10个语句占全部内催读取量的比例

select sum(pct_bufgets)

from (select rank() over(order by buffer_gets desc) as rank_bufgets,

to_char(100 * ratio_to_report(buffer_gets) over(), '999.99') pct_bufgets

from v$sqlarea)

where rank_bufgets < 11;

--最应该优化的25个SQL

select * from (

SELECT buffer_gets,sql_text,rownum rn from v$sqlarea order by buffer_gets desc )

where rn<26;

--固定缓存对象

select *

from v$db_object_cache

where sharable_mem > 100000

and type in ('PACKAGE', 'PACKAGE BODY', 'PROCEDURE', 'FUNCTION');

--磁盘评估

---调整表和索引 表和索引不要在同一个表空间中

select i.index_name, t.table_name, t.tablespace_name

from user_tables t, user_indexes i

where t.table_name = i.table_name

and t.tablespace_name = i.tablespace_name;

--表的行链接问题

select count(*) chained_rows, table_name

from chained_rows

group by table_name;

--关键文件路径

select file_name, tablespace_name, bytes

from dba_data_files

union all

select file_name, tablespace_name, bytes

from dba_temp_files

union all

select name file_name, null, null

from v$controlfile

union all

select member file_name, to_char(a.group#) tablespace_name, b.bytes bytes

from v$logfile a, v$log b

where a.group# = b.group#

union all (select value file_name, null, null

from v$parameter

where name like 'log_archive_dest_%'

and value is not null

minus

select value file_name, null, null

from v$parameter

where name like 'log_archive_dest_state%');

--回滚段平衡

select name,value from v$parameter where name like '%undo_%';

select a.name,

b.extents,

b.rssize,

b.xacts,

b.waits,

b.gets optsize,

status

from v$rollname a, v$rollstat b

where a.usn = b.usn;

--磁盘排序

select name,value from v$sysstat where name like '%sorts%';

--最浪费磁盘读操作的前10个语句占用所有语句的比例

select sum(pct_bufgets)

from (select rank() over(order by disk_reads desc) as rank_bufgets,

to_char(100 * ratio_to_report(disk_reads) over() , '999.99') pct_bufgets from v$sqlarea)

where rank_bufgets < 11;

--前25个最浪费磁盘读操作的SQL

select *

from (select executions,

disk_reads,

substr(sql_text, 1, 4000),

rownum rn

from v$sqlarea

order by disk_reads desc)

where rn < 26;

--字典管理表控件中的EXTENT总数不超过4096

select a.tablespace_name ,sum(a.extents)

from dba_segments a ,dba_tablespaces b

where a.tablespace_name=b.tablespace_name

and b.extent_management ='DICTIONARY'

group by a.tablespace_name

order by sum(a.extents)