Oracle优化 -- 关于Database Buffer Cache相关参数DB_CACHE_SIZE的优化设置
select size_for_estimate, buffers_for_estimate ,ESTD_PHYSICAL_READ_factor,ESTD_PHYSICAL_READS from v$db_cache_advice?
? 2????? where block_size='8192' and advice_status='ON';
中，size_for_estimate表示預計的數據庫高速緩沖區的大小（即：db_cache_size的值）。ESTD_PHYSICAL_READS表示預計的物理讀。
當增加數據庫高速緩沖區的的時候，物理讀（ESTD_PHYSICAL_READS）越少，說明命中率越高。
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1.優化緩沖區大小、提高服務器的命中率
db_cache_size??????????????????????? big integer 838860800
2.查看緩沖區命中率是否需要調優.
select 1 - ((physical.value - direct.value - lobs.value) / logical.value)
???? "Buffer Cache Hit Ratio"
? from v$sysstat physical,v$sysstat direct,v$sysstat lobs,v$sysstat logical
? where physical.name = 'physical reads'
? and direct.name='physical reads direct'
? and lobs.name='physical reads direct (lob)'
? and logical.name='session logical reads';
當命中率>90%說明命中率很高了
3。獲取推薦的值
select name,size_for_estimate,v$db_cache_advice.ESTD_PHYSICAL_READS from v$db_cache_advice?
where block_size='8192' and advice_status='ON';
set linesize 1000
---20100619Oracle9i數據 Solaris 9i操作系統
SQL> set linesize 1000
SQL> select size_for_estimate, buffers_for_estimate ,ESTD_PHYSICAL_READ_factor,ESTD_PHYSICAL_READS from v$db_cache_advice?
??? where block_size='8192' and advice_status='ON';
SIZE_FOR_ESTIMATE BUFFERS_FOR_ESTIMATE ESTD_PHYSICAL_READ_FACTOR ESTD_PHYSICAL_READS
----------------- -------------------- ------------------------- -------------------
?????????????? 80???????????????? 9925?????????????????? 28.9757????????? 1436311200
????????????? 160??????????????? 19850??????????????????? 2.1053?????????? 104360120
????????????? 240??????????????? 29775??????????????????? 1.5819??????????? 78413087
????????????? 320??????????????? 39700??????????????????? 1.4262??????????? 70693980
????????????? 400??????????????? 49625??????????????????? 1.3543??????????? 67131735
????????????? 480??????????????? 59550???????????????????? 1.278??????????? 63349434
????????????? 560??????????????? 69475??????????????????? 1.1893??????????? 58954568
????????????? 640??????????????? 79400??????????????????? 1.1325??????????? 56135206
????????????? 720??????????????? 89325??????????????????? 1.0762??????????? 53347837
????????????? 800??????????????? 99250???????????????????????? 1??????????? 49569438
????????????? 880?????????????? 109175???????????????????? .7067??????????? 35030953
SIZE_FOR_ESTIMATE BUFFERS_FOR_ESTIMATE ESTD_PHYSICAL_READ_FACTOR ESTD_PHYSICAL_READS
----------------- -------------------- ------------------------- -------------------
????????????? 960?????????????? 119100???????????????????? .3991??????????? 19784701
???????????? 1040?????????????? 129025???????????????????? .2305??????????? 11423374
???????????? 1120?????????????? 138950???????????????????? .1927???????????? 9552903
???????????? 1200?????????????? 148875???????????????????? .1506???????????? 7466278
???????????? 1280?????????????? 158800???????????????????? .1501???????????? 7438186
???????????? 1360?????????????? 168725???????????????????? .1501???????????? 7438186
???????????? 1440?????????????? 178650???????????????????? .1501???????????? 7438186
???????????? 1520?????????????? 188575???????????????????? .1501???????????? 7438186
???????????? 1600?????????????? 198500???????????????????? .1501???????????? 7438186
SIZE_FOR_ESTIMATE? M 為單位：
當SIZE_FOR_ESTIMATE=80M 的時候 ESTD_PHYSICAL_READS=1436311200
當SIZE_FOR_ESTIMATE=1120M 的時候 ESTD_PHYSICAL_READS=9552903
當SIZE_FOR_ESTIMATE=1280M 的時候 ESTD_PHYSICAL_READS=7438186
之后ESTD_PHYSICAL_READS固定了
所以應該過大db_cache_size=1120M的值使得
4.修改發現DB_cache_size太大了。過大SGA區域解決
alter system set db_cache_size=1120M
--sga設置太小了導致
SQL>? alter system set db_cache_size=1120M;
alter system set db_cache_size=1120M
*
ERROR 位于第 1 行:
ORA-02097: 無法修改參數，因為指定的值無效
ORA-00384: 沒有足夠的內存來增加高速緩存的大小
之前的值
sga_max_size???????????????????????? big integer 1494715120
SQL>alter system set SGA_MAX_SIZE=3500M scope=spfile;
系統已更改。
重新啟動與關閉解決
SQL> shutdown immediate
數據庫已經關閉。
已經卸載數據庫。
ORACLE 例程已經關閉。
SQL> startup
ORACLE 例程已經啟動。
Total System Global Area 3675756336 bytes
Fixed Size?????????????????? 735024 bytes
Variable Size??????????? 2835349504 bytes
Database Buffers????????? 838860800 bytes
Redo Buffers???????????????? 811008 bytes
數據庫裝載完畢。
數據庫已經打開。
查看命中率\當前只有80的滿足要求
SQL> select size_for_estimate, buffers_for_estimate ,ESTD_PHYSICAL_READ_factor,ESTD_PHYSICAL_READS from v$db_cache_advice
? 2????? where block_size='8192' and advice_status='ON';
SIZE_FOR_ESTIMATE BUFFERS_FOR_ESTIMATE ESTD_PHYSICAL_READ_FACTOR ESTD_PHYSICAL_READS
----------------- -------------------- ------------------------- -------------------
?????????????? 80???????????????? 9925???????????????????????? 1??????????????? 1528
????????????? 160??????????????? 19850???????????????????????? 1??????????????? 1528
????????????? 240??????????????? 29775???????????????????????? 1??????????????? 1528
????????????? 320??????????????? 39700???????????????????????? 1??????????????? 1528
????????????? 400??????????????? 49625???????????????????????? 1??????????????? 1528
????????????? 480??????????????? 59550???????????????????????? 1??????????????? 1528
????????????? 560??????????????? 69475???????????????????????? 1??????????????? 1528
????????????? 640??????????????? 79400???????????????????????? 1??????????????? 1528
????????????? 720??????????????? 89325???????????????????????? 1??????????????? 1528
????????????? 800??????????????? 99250???????????????????????? 1??????????????? 1528
????????????? 880?????????????? 109175???????????????????????? 1??????????????? 1528
SIZE_FOR_ESTIMATE BUFFERS_FOR_ESTIMATE ESTD_PHYSICAL_READ_FACTOR ESTD_PHYSICAL_READS
----------------- -------------------- ------------------------- -------------------
????????????? 960?????????????? 119100???????????????????????? 1??????????????? 1528
???????????? 1040?????????????? 129025???????????????????????? 1??????????????? 1528
???????????? 1120?????????????? 138950???????????????????????? 1??????????????? 1528
???????????? 1200?????????????? 148875???????????????????????? 1??????????????? 1528
???????????? 1280?????????????? 158800???????????????????????? 1??????????????? 1528
???????????? 1360?????????????? 168725???????????????????????? 1??????????????? 1528
???????????? 1440?????????????? 178650???????????????????????? 1??????????????? 1528
???????????? 1520?????????????? 188575???????????????????????? 1??????????????? 1528
???????????? 1600?????????????? 198500???????????????????????? 1??????????????? 1528
命中率降低了？????????
??? SQL> select 1 - ((physical.value - direct.value - lobs.value) / logical.value)
? 2?????? "Buffer Cache Hit Ratio"
? 3??? from v$sysstat physical,v$sysstat direct,v$sysstat lobs,v$sysstat logical
? 4??? where physical.name = 'physical reads'
? 5??? and direct.name='physical reads direct'
? 6??? and lobs.name='physical reads direct (lob)'
? 7??? and logical.name='session logical reads';
Buffer Cache Hit Ratio
----------------------
??????????? .906673167
繼續縮小SGA大小
SQL>alter system set SGA_MAX_SIZE=3000M scope=spfile;
SQL> shutdown immediate
數據庫已經關閉。
已經卸載數據庫。
ORACLE 例程已經關閉。
SQL> startup
ORACLE 例程已經啟動。
Total System Global Area 3155661888 bytes
Fixed Size?????????????????? 734272 bytes
Variable Size??????????? 2315255808 bytes
Database Buffers????????? 838860800 bytes
Redo Buffers???????????????? 811008 bytes
數據庫裝載完畢。
數據庫已經打開。
select size_for_estimate, buffers_for_estimate ,ESTD_PHYSICAL_READ_factor,ESTD_PHYSICAL_READS from v$db_cache_advice?
??? where block_size='8192' and advice_status='ON';
繼續測試：等待30分鐘之后測試
??? SQL> alter system set db_cache_size=1120M;
???
??? select 1 - ((physical.value - direct.value - lobs.value) / logical.value)
???? "Buffer Cache Hit Ratio"
? from v$sysstat physical,v$sysstat direct,v$sysstat lobs,v$sysstat logical
? where physical.name = 'physical reads'
? and direct.name='physical reads direct'
? and lobs.name='physical reads direct (lob)'
? and logical.name='session logical reads';
? ---命中率逐漸的提高了
? ---半個小時之后查詢命中率是98%
? SQL> select 1 - ((physical.value - direct.value - lobs.value) / logical.value)
? 2?????? "Buffer Cache Hit Ratio"
? 3??? from v$sysstat physical,v$sysstat direct,v$sysstat lobs,v$sysstat logical
? 4??? where physical.name = 'physical reads'
? 5??? and direct.name='physical reads direct'
? 6??? and lobs.name='physical reads direct (lob)'
? 7??? and logical.name='session logical reads';
Buffer Cache Hit Ratio
----------------------
??????????? .980309028
-----查詢推薦的值
show parameter db_block_size
8192
select name,size_for_estimate,v$db_cache_advice.ESTD_PHYSICAL_READS from
v$db_cache_advice? where block_size='8192' and advice_status='ON';
NAME???????????????? SIZE_FOR_ESTIMATE ESTD_PHYSICAL_READS
-------------------- ----------------- -------------------
DEFAULT??????????????????????????? 112??????????????? 9581
DEFAULT??????????????????????????? 224??????????????? 9514
DEFAULT??????????????????????????? 336??????????????? 9514
DEFAULT??????????????????????????? 448??????????????? 9514
DEFAULT??????????????????????????? 560??????????????? 9514
DEFAULT??????????????????????????? 672??????????????? 9514
DEFAULT??????????????????????????? 784??????????????? 9514
DEFAULT??????????????????????????? 896??????????????? 9514
DEFAULT?????????????????????????? 1008??????????????? 9514
DEFAULT?????????????????????????? 1120??????????????? 9514
DEFAULT?????????????????????????? 1232??????????????? 9514
NAME???????????????? SIZE_FOR_ESTIMATE ESTD_PHYSICAL_READS
-------------------- ----------------- -------------------
DEFAULT?????????????????????????? 1344??????????????? 9514
DEFAULT?????????????????????????? 1456??????????????? 9514
DEFAULT?????????????????????????? 1568??????????????? 9514
DEFAULT?????????????????????????? 1680??????????????? 9514
DEFAULT?????????????????????????? 1792??????????????? 9514
DEFAULT?????????????????????????? 1904??????????????? 9514
DEFAULT?????????????????????????? 2016??????????????? 9514
DEFAULT?????????????????????????? 2128??????????????? 9514
DEFAULT?????????????????????????? 2240??????????????? 9514
顯示只要112M大小的空間就可以穩定降低ESTD_PHYSICAL_READS
alter system set db_cache_size=112M
NAME???????????????? SIZE_FOR_ESTIMATE ESTD_PHYSICAL_READS
-------------------- ----------------- -------------------
DEFAULT???????????????????????????? 16?????????????????? 0
DEFAULT???????????????????????????? 32?????????????????? 0
DEFAULT???????????????????????????? 48?????????????????? 0
DEFAULT???????????????????????????? 64?????????????????? 0
DEFAULT???????????????????????????? 80?????????????????? 0
DEFAULT???????????????????????????? 96?????????????????? 0
DEFAULT??????????????????????????? 112?????????????????? 0
DEFAULT??????????????????????????? 128?????????????????? 0
DEFAULT??????????????????????????? 144?????????????????? 0
DEFAULT??????????????????????????? 160?????????????????? 0
DEFAULT??????????????????????????? 176?????????????????? 0
NAME???????????????? SIZE_FOR_ESTIMATE ESTD_PHYSICAL_READS
-------------------- ----------------- -------------------
DEFAULT??????????????????????????? 192?????????????????? 0
DEFAULT??????????????????????????? 208?????????????????? 0
DEFAULT??????????????????????????? 224?????????????????? 0
DEFAULT??????????????????????????? 240?????????????????? 0
DEFAULT??????????????????????????? 256?????????????????? 0
DEFAULT??????????????????????????? 272?????????????????? 0
DEFAULT??????????????????????????? 288?????????????????? 0
DEFAULT??????????????????????????? 304?????????????????? 0
DEFAULT??????????????????????????? 320?????????????????? 0
---查看命中率
? select 1 - ((physical.value - direct.value - lobs.value) / logical.value)
???? "Buffer Cache Hit Ratio"
? from v$sysstat physical,v$sysstat direct,v$sysstat lobs,v$sysstat logical
? where physical.name = 'physical reads'
? and direct.name='physical reads direct'
? and lobs.name='physical reads direct (lob)'
? and logical.name='session logical reads';
Buffer Cache Hit Ratio
----------------------
??????????? .982795739
說明Oracle更換峰值的情況決定db_cache_size的大小。
所以設置最大峰值滿足的情況。
alter system set db_cache_size=1120M;滿足峰值的時候最大值
select name,size_for_estimate,v$db_cache_advice.ESTD_PHYSICAL_READS from
v$db_cache_advice? where block_size='8192' and advice_status='ON';
oracle10g Solaris 10 sparc系統調整
--查
? select name,size_for_estimate,v$db_cache_advice.ESTD_PHYSICAL_READS from
v$db_cache_advice? where block_size='8192' and advice_status='ON';
-------------------- ----------------- -------------------
DEFAULT??????????????????????????? 128???????????? 1206647
DEFAULT??????????????????????????? 256???????????? 1067789
DEFAULT??????????????????????????? 384????????????? 987752
DEFAULT??????????????????????????? 512????????????? 965164
DEFAULT??????????????????????????? 640????????????? 913815
DEFAULT??????????????????????????? 768????????????? 893485
DEFAULT??????????????????????????? 896????????????? 867321
DEFAULT?????????????????????????? 1024????????????? 808884
DEFAULT?????????????????????????? 1152????????????? 599909
DEFAULT?????????????????????????? 1280????????????? 344618
--此時開始保持在一個穩定的讀取值
alter system set db_cache_size=1196M
DEFAULT?????????????????????????? 1296????????????? 321763
NAME???????????????? SIZE_FOR_ESTIMATE ESTD_PHYSICAL_READS
-------------------- ----------------- -------------------
DEFAULT?????????????????????????? 1408????????????? 285030
DEFAULT?????????????????????????? 1536????????????? 280506
DEFAULT?????????????????????????? 1664????????????? 280325
DEFAULT?????????????????????????? 1792????????????? 279816
DEFAULT?????????????????????????? 1920????????????? 266871
DEFAULT?????????????????????????? 2048????????????? 235838
DEFAULT?????????????????????????? 2176????????????? 231298
DEFAULT?????????????????????????? 2304????????????? 228483
DEFAULT?????????????????????????? 2432????????????? 224971
DEFAULT?????????????????????????? 2560????????????? 219467
--修改
alter system set db_cache_size=1196M
--查看命中率
? select 1 - ((physical.value - direct.value - lobs.value) / logical.value)
???? "Buffer Cache Hit Ratio"
? from v$sysstat physical,v$sysstat direct,v$sysstat lobs,v$sysstat logical
? where physical.name = 'physical reads'
? and direct.name='physical reads direct'
? and lobs.name='physical reads direct (lob)'
? and logical.name='session logical reads';
轉載于:https://www.cnblogs.com/login2012/p/5752687.html
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