OracleORACLE ASMM与AMM的总括

 

概念比较介绍

 

深信有些人会对ORACLE当中的AMM(Automatic
Memory Management)与ASMM(Automatic Shared Memory
Management)有些迷惑或歪曲,不清楚两者的异同,本文会从多少个地方来总计一下双边的异议。如有不足或疏漏之处,敬请指正!

 

从ORACLE公布的本子历史(时间轴)来看,ORACLE的内存管理的大概历程如下:

 

ORACLE  9i 
    
PGA自动管理,SGA手动管理

ORACLE
10g      PGA自动管理,SGA自动管理(ASMM,自动共享内存管理)

ORACLE
11g      PGA,SGA统一机动管理(AMM,自动内存管理)

ORACLE
12c      跟11g一律,没有变化

 

 

合法文档的介绍资料如下:

 

·        
Oracle
9i

 

·        
Beginning
with Oracle9i, the dynamic SGA infrastructure allowed for the sizing of
the Buffer Cache, Shared Pool and the Large Pool without having to shut
down the database. Key features being:

o   Dynamic
Memory resizing

o   DB_CACHE_SIZE
instead of DB_BLOCK_BUFFERS

o   DB_nK_CACHE_SIZE
for multiple block sizes

o   PGA_AGGREGATE_TARGET
Introduction of Automatic PGA Memory management

 

·        
Oracle
Database 10g

 

·        
Automatic
Shared Memory Management (ASMM) was introduced in 10g. You enable the
automatic shared memory management feature by setting the SGA_TARGET
parameter to a non-zero value.

 

·        
Oracle
Database 11g

 

·        
Automatic
Memory Management is being introduced in 11g. This enables automatic
tuning of PGA and SGA with use of two new parameters named
MEMORY_MAX_TARGET and MEMORY_TARGET

·        
Oracle
Database 12c

           
Automatic Memory Management keeps the same behaviour as in 11g.

 

 

机关共享内存管理(Automatic
Shared Memory Management ASMM)是ORACLE
10g启幕引入的的新技巧,ASMM用来贯彻SGA的机关管理。。当启用自动共享内存管理后,不再需要为各类内存组件设定值,当然假设您设置SGA_TARGET的同时,设置了db_cache_size、shared_pool_size那多少个参数,那么db_cache_size、shared_pool_size这多少个参数值会作为最小值要求。官方关于Automatic
Shared Memory Management的牵线如下:

 

Automatic
Shared Memory Management

 

In
previous database releases, a database administrator (DBA) was required
to manually specify different SGA component sizes by setting a number of
initialization parameters, including the SHARED_POOL_SIZE,
DB_CACHE_SIZE, JAVA_POOL_SIZE, and LARGE_POOL_SIZE parameters.
Oracle Database 10g includes the Automatic Shared Memory Management
feature which simplifies the SGA memory management significantly. In
Oracle Database 10g, a DBA can simply specify the total amount of SGA
memory available to an instance using the SGA_TARGET initialization
parameter and the Oracle Database will automatically distribute this
memory among various subcomponents to ensure most effective memory
utilization.

 

When
automatic SGA memory management is enabled, the sizes of the different
SGA components are flexible and can adapt to the needs of a workload
without requiring any additional configuration. The database
automatically distributes the available memory among the various
components as required, allowing the system to maximize the use of all
available SGA memory.

 

ORACLE
10G本子开端推出了ASMM,自动SGA管理,它的产出一定水准上襄助DBA解决了管住SGA的问题,通过设置参数SGA_TARGET来控制ASMM,其中SGA_TARGET为零代表禁用ASMM,非零值表示启用ASMM。不过在10G
R1等中期版本,ASMM还不够成熟,而且存在相比多的BUG,导致了相比较多的题材。在ORACLE
10g R2后续版本中,ASMM才逐步完善并成熟。

 

到了11g未来,ORACLE又实现了PGA和SGA的统一机动管理
,那么些名为自动化内存管理(Automatic Memory
Management,AMM)。从这一个演变历程来看,ORACLE从最初叶的手动配置各种零部件参数,逐渐逐步向智能化、傻瓜化、自动化的倾向稳步前进。这个是一个一定的历史趋势。关于AMM的法定文档介绍如下:

 

About
Automatic Memory Management

 

The
simplest way to manage instance memory is to allow the Oracle Database
instance to automatically manage and tune it for you. To do so (on most
platforms), you set only a target memory size initialization parameter
(MEMORY_TARGET) and optionally a maximum memory size initialization
parameter (MEMORY_MAX_TARGET). The instance then tunes to the target
memory size, redistributing memory as needed between the system global
area (SGA) and the instance program global area (instance PGA). Because
the target memory initialization parameter is dynamic, you can change
the target memory size at any time without restarting the database. The
maximum memory size serves as an upper limit so that you cannot
accidentally set the target memory size too high, and so that enough
memory is set aside for the Oracle Database instance in case you do want
to increase total instance memory in the future. Because certain SGA
components either cannot easily shrink or must remain at a minimum size,
the instance also prevents you from setting the target memory size too
low.

 

If
you create your database with Database Configuration Assistant (DBCA)
and choose the basic installation option, automatic memory management is
enabled. If you choose advanced installation, Database Configuration
Assistant (DBCA) enables you to select automatic memory
management.

 

 

 

ORACLE
11g AMM 的引入, 组合出来有 5 种内存管理情势.

 

   
自动内存管理(AMM)   :
memory_target=非0,是机关内存管理,即便开头化参数 LOCK_SGA=TRUE,则
AMM 是不可用的。

   
自动共享内存管理(ASMM): 在memory_target=0 and
sga_target为非0的状态下是电动内存管理

   
手工共享内存管理      : memory_target=0 and
sga_target=0 
指定
share_pool_size 、db_cache_size 等 sga 参数

    自动 PGA
管理         : memory_target=0 and
workarea_size_policy=auto 
and PGA_AGGREGATE_TARGET=值

    手动 PGA
管理         : memory_target=0 and
workarea_size_policy=manal 
然后指定 SORT_AREA_SIZE 等 PGA 参数,一般不应用手动管理PGA。

 

 

Oracle
Database 11g

supports various memory management methods, which are chosen by
initialization parameter settings. Oracle recommends that you enable the
automatic memory management method.

 

 

  1. Automatic
    Memory Management – For Both the SGA and Instance PGA

  1. Automatic
    Shared Memory Management – For the SGA

  1. Manual
    Shared Memory Management – For the SGA

  1. Automatic
    PGA Memory Management –For the Instance PGA

  1. Manual
    PGA Memory Management – For the Instance PGA

 

 

 

 

 

ASMM切换到AMM

 

一般来说所示,当前试行环境下活动内存管理已被剥夺(memory_target=0)

 

SQL> select * from v$version;

 

BANNER

--------------------------------------------------------------------------------

Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production

PL/SQL Release 11.2.0.1.0 - Production

CORE    11.2.0.1.0      Production

TNS for Linux: Version 11.2.0.1.0 - Production

NLSRTL Version 11.2.0.1.0 - Production

 

SQL> show parameter memory_target ;

 

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

memory_target                        big integer 0

SQL> show parameter memory_max_target;

 

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

memory_max_target                    big integer 0

SQL> 

SQL> show parameter sga;

 

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

lock_sga                             boolean     FALSE

pre_page_sga                         boolean     FALSE

sga_max_size                         big integer 1G

sga_target                           big integer 1G

 

 

在11g中,假若运用ASMM,对应的内存共享段是真正的共享段。

 

SQL> !

[oracle@DB-Server ~]$ ipcs -m

 

------ Shared Memory Segments --------

key        shmid      owner      perms      bytes      nattch     status      

0x00000000 4128770    root      644        80         2                       

0x00000000 4161540    root      644        16384      2                       

0x00000000 4194309    root      644        280        2                       

0xfc5d1940 7012369    oracle    660        1075838976 49     

 

 

如下所示,首先检查参数文件类型,然后修改参数sga_target、memory_max_target、memory_target。因为中间有些参数为静态参数,所以在修改参数后,需要重启数据库。

 

 

 

SQL> show parameter spfile;

 

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

spfile                               string      /u01/app/oracle/product/11.1.0

                                                 /dbhome_1/dbs/spfilegsp.ora

SQL> alter system set sga_max_size=0 scope=spfile;

 

System altered.

 

SQL> alter system set sga_target=0 scope=spfile;

 

System altered.

 

SQL> alter system set pga_aggregate_target=0 scope=spfile;

 

 

SQL> alter system set memory_max_target=1G scope=spfile;

 

System altered.

 

SQL> alter system set memory_target=1G scope=spfile;

 

System altered.

 

SQL> 

 

重启数据库后,检查对应参数。

 

SQL> shutdown immediate;

Database closed.

Database dismounted.

ORACLE instance shut down.

SQL> startup

ORACLE instance started.

 

Total System Global Area  517816320 bytes

Fixed Size                  2214776 bytes

Variable Size             159384712 bytes

Database Buffers          348127232 bytes

Redo Buffers                8089600 bytes

Database mounted.

SQL> show parameter memory

 

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

hi_shared_memory_address             integer     0

memory_max_target                    big integer 1G

memory_target                        big integer 1G

shared_memory_address                integer     0

SQL> 

 

自行内存管理(AMM)启动以后,系统共享段变为“虚拟”共享段。

 

[oracle@DB-Server ~]$ ipcs -m

 

------ Shared Memory Segments --------

key        shmid      owner      perms      bytes      nattch     status      

0x00000000 4128770    root      644        80         2                       

0x00000000 4161540    root      644        16384      2                       

0x00000000 4194309    root      644        280        2                       

0xfc5d1940 7077905    oracle    660        4096       0            

 

 

 

 

 

11g
MEMORY_TARGET Parameter Dependency

 

那么有个疑问,自动内存管理(AMM)格局下边,sga_max_size、sga_target、memory_max_target、memory_target、pga_aggregate_target这么些参数的关联是何等的吧?其实官方文档已经有详尽阐释

 

If
MEMORY_TARGET is set to a non-zero value:

 

·        
If
SGA_TARGET and PGA_AGGREGATE_TARGET are set, they will be considered
the minimum values for the sizes of SGA and the PGA respectively.
MEMORY_TARGET values can range from SGA_TARGET +
PGA_AGGREGATE_TARGET to MEMORY_MAX_TARGET.

·        
If
SGA_TARGET is set and PGA_AGGREGATE_TARGET is not set, we will still
auto-tune both parameters. PGA_AGGREGATE_TARGET will be initialized to
a value of MEMORY_TARGET – SGA_TARGET.

Oracle,·        
If
PGA_AGGREGATE_TARGET is set and SGA_TARGET is not set, we will still
auto-tune both parameters. SGA_TARGET will be initialized to the
minimum non-zero value of MEMORY_TARGET – PGA_AGGREGATE_TARGET and
SGA_MAX_SIZE and will auto tune its components.

·        
If
neither is set, they will be auto-tuned without any minimum or default
values. We will have a policy of distributing the total memory set by
MEMORY_TARGET parameter in a fixed ratio to the the SGA and PGA during
initialization. The policy is to give 60% to the SGA and 40% to the PGA
at startup.

 

If
MEMORY_MAX_TARGET has not been explicitly set, but MEMORY_TARGET has,
the instance automatically sets MEMORY_MAX_TARGET to the same value as
MEMORY_TARGET. If MEMORY_TARGET has not been explicitly set, but
MEMORY_MAX_TARGET has, then MEMORY_TARGET defaults to 0. After
instance startup, it then is possible to dynamically change
MEMORY_TARGET to a non-zero value, provided that it does not exceed the
value of MEMORY_MAX_TARGET.

 

If
MEMORY_TARGET is not set or set to set to 0 explicitly (default value
is 0 for 11g):

·        
If
SGA_TARGET is set we will only auto-tune the sizes of the components of
the SGA. PGA will be autotuned independent of whether it is explicitly
set or not. However, the combination of SGA and PGA will not be
auto-tuned, i.e. the SGA and PGA will not share memory and resize as
with the case of MEMORY_TARGET being set to a non-zero value.

·        
If
neither SGA_TARGET nor PGA_AGGREGATE_TARGET is set, we will follow
the same policy as we have today; PGA will be auto-tuned and the SGA
will not be auto-tuned and parameters for some of the SGA components
will have to be set explicitly (for SGA_TARGET).

·        
If
only MEMORY_MAX_TARGET is set, MEMORY_TARGET will default to 0 and we
will not auto tune the SGA and PGA. It will default to 10gR2
behavior.

·        
If
SGA_MAX_SIZE is not user set, it is internally set to
MEMORY_MAX_TARGET.

 

大家下面仍然通过试验一一验证一下:

 

1:当MEMORY_TARGET大于0的意况下,可以设置SGA_TARGET、PGA_AGGREGATE_TARGET的值为非0,对应的意义分别如下:

 

   
假若设置了SGA_TARGET和PGA_AGGREGATE_TARGET,它们分别表示SGA的的最小值和PGA的细小值。MEMORY_TARGET值的限定可以从SGA_TARGET

  • PGA_AGGREGATE_TARGET到MEMORY_MAX_TARGET。

    当然SGA_TARGET + PGA_AGGREGATE_TARGET的和必须低于等于memory_target,另外,如若还要安装了sga_target、pga_aggregate_target的值,memory_target的值必须超出等于sga_target与pga_aggregate_target之和。如下测试所示:

 

SQL> alter system set pga_aggregate_target=200m scope=both;

 

System altered.

 

SQL> show parameter pga_aggregate_target;

 

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

pga_aggregate_target                 big integer 200M

SQL> 

 

 

SQL> show parameter sga;

 

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

lock_sga                             boolean     FALSE

pre_page_sga                         boolean     FALSE

sga_max_size                         big integer 496M    #后面讲述为什么sga_max_size为什么没有被置为0

sga_target                           big integer 0

SQL> alter system set sga_target=400m scope=both;

 

System altered.

 

SQL> show parameter sga;

 

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

lock_sga                             boolean     FALSE

pre_page_sga                         boolean     FALSE

sga_max_size                         big integer 496M

sga_target                           big integer 400M

SQL> 

Oracle 1

 

 

 

SQL> show parameter sga;

 

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

lock_sga                             boolean     FALSE

pre_page_sga                         boolean     FALSE

sga_max_size                         big integer 496M

sga_target                           big integer 400M

SQL> show parameter pga_aggregate_target;

 

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

pga_aggregate_target                 big integer 200M

SQL> alter system set memory_target=696m scope=both;

 

System altered.

 

SQL> alter system set memory_target=600m scope=both;

 

System altered.

 

SQL> alter system set memroy_target=500m scope=both;

alter system set memroy_target=500m scope=both

                 *

ERROR at line 1:

ORA-02065: illegal option for ALTER SYSTEM

 

 

SQL>  alter system set memory_target=500m scope=both;

 alter system set memory_target=500m scope=both

*

ERROR at line 1:

ORA-02097: parameter cannot be modified because specified value is invalid

ORA-00838: Specified value of MEMORY_TARGET is too small, needs to be at least 600M

 

Oracle 2

 

 

SQL> show parameter memory_target;

 

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

memory_target                        big integer 600M

SQL> show parameter sga;

 

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

lock_sga                             boolean     FALSE

pre_page_sga                         boolean     FALSE

sga_max_size                         big integer 496M

sga_target                           big integer 400M

SQL> show parameter pga

 

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

pga_aggregate_target                 big integer 200M

SQL> 

SQL> 

SQL> alter system set pga_aggregate_target=201m scope=both;

alter system set pga_aggregate_target=300m scope=both

*

ERROR at line 1:

ORA-02097: parameter cannot be modified because specified value is invalid

ORA-00840: PGA_AGGREGATE_TARGET cannot be modified to the specified value

 

如上测试所示,若是设置了pga_aggregate_target和sga_target,那么pga_aggregate_target

  • sga_target
    必须低于等于memory_target,另外,memory_target也不可能不高于等于(pga_aggregate_target
  • sga_target)

 

假诺设置了SGA_TARGET并且PGA_AGGREGATE_TARGET没有安装,数据库仍旧会活动调整这五个参数。
PGA_AGGREGATE_TARGET将被开端化为MEMORY_TARGET –
SGA_TARGET的值。

假若设置了PGA_AGGREGATE_TARGET并且没有设置SGA_TARGET,数据库依然会自行调整这七个参数。
SGA_TARGET将被开端化为MEMORY_TARGET –
PGA_AGGREGATE_TARGET,并在这个值和SGA_MAX_SIZE这么些间隔范围内活动调整

如果SGA_TARGET和PGA_AGGREGATE_TARGET两者都未曾设置的话,则它们将被自动调谐而从未其它最小值或默认值。 我们将有一个方针,在起先化过程中,将由MEMORY_TARGET参数设置的总内存以固定的比重分红给SGA和PGA。 政策是在启动时给予SGA
60%和PGA 40%给PGA。

 

 

2:
没有设置SGA_MAX_SIZE,不过为啥SGA_MAX_SIZE从来有值,尽管将其安装为0或使用reset
alter system set sga_max_size=0 scope=spfile; SGA_MAX_SIZE一贯有值。官方关于SGA_MAX_SIZE的牵线如下:

 

 

SGA_MAX_SIZE
specifies the maximum size of the SGA for the lifetime of the
instance.

On
64-bit platforms and non-Windows 32-bit platforms, when either
MEMORY_TARGET or MEMORY_MAX_TARGET is specified, the default value of
SGA_MAX_SIZE is set to the larger of the two parameters. This causes
more address space to be reserved for expansion of the SGA.

On
Windows 32-bit platforms, the default value of SGA_MAX_SIZE is the
largest of the following values:

·        
 

·        
60%
of MEMORY_TARGET, if specified

·        
 

·        
60%
of MEMORY_MAX_TARGET, if specified

·        
 

·        
25%
of the total available virtual address space

 

也就是说在64位平台和非Windows 32位平台上,当指定MEMORY_TARGET或MEMORY_MAX_TARGET时,SGA_MAX_SIZE的默认值将设置为两个参数中较大的一个。 这导致更多的地址空间被保留用于SGA的扩展。

这也是之前一直让我迷惑的地方。另外,官方文档建议:当切换到AMM,即使用MEMORY_TARGET时,不应该设置参数SGA_MAX_SIZE(用于ASMM),因为这样做会修复SGA的大

小,因此与MEMORY_TARGET的预期用法相冲突。(原文:Check also for SGA_MAX_SIZE being set. When switching to AMM, i.e. using MEMORY_TARGET,

the parameter SGA_MAX_SIZE (used for ASMM) should not be set as doing so fixes the size of the SGA, and hence conflicts

with the intended use of MEMORY_TARGET.)

 

 

Oracle 3

 

   

SGA_MAX_SIZE的值最好不要去修改,假设其值领先MEMORY_MAX_TARGET的话,就报ORA-00844 & ORA-00851
错误。如下所示

 

SQL> alter system set sga_max_size=1025M scope=spfile;

 

System altered.

SQL> shutdown immediate;

Database closed.

Database dismounted.

ORACLE instance shut down.

SQL> startup

ORA-00844: Parameter not taking MEMORY_TARGET into account

ORA-00851: SGA_MAX_SIZE 1090519040 cannot be set to more than MEMORY_TARGET 637534208.

SQL> 

 

 

这儿急需扭转对应spfile的pfile文件,然后找到*.sga_max_size这多少个值,删除后再一次生成对应的spfile,启动数据库实例即可,当然你也可以设置其值超过MEMORY_TARGET即可。

 

 

AMM切换到ASMM

 

SQL> show parameter target;

 

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

archive_lag_target                   integer     0

db_flashback_retention_target        integer     1440

fast_start_io_target                 integer     0

fast_start_mttr_target               integer     0

memory_max_target                    big integer 1552M

memory_target                        big integer 1552M

parallel_servers_target              integer     16

pga_aggregate_target                 big integer 0

sga_target                           big integer 0

SQL> alter system set memory_max_target=0 scope=spfile;

 

System altered.

 

SQL> alter system set memory_target=0 scope=spfile;

 

System altered.

 

SQL> alter system set pga_aggregate_target=200m scope=spfile;

 

System altered.

 

SQL> alter system set sga_max_size=1g scope=spfile;

 

System altered.

 

SQL> alter system set sga_target=1g scope=spfile;

 

System altered.

 

SQL> 

 

 

SQL> startup

ORA-00843: Parameter not taking MEMORY_MAX_TARGET into account

ORA-00849: SGA_TARGET 1073741824 cannot be set to more than MEMORY_MAX_TARGET 0.

SQL> 

 

变更对应的spfile的pfile文件,然后删除memory_max_target和memory_target多个参数后,然后生成对应的spfile,最终重启数据库实例即可。

 

SQL>
create pfile from spfile;

 

File
created.

 

 

*.memory_max_target=0

*.memory_target=0

 

SQL>
create spfile from pfile;

 

File
created.

 

SQL>

 

 

选择AMM还是HugePages

 

ORACLE
11g始于推出AMM,它是ORACLE在ASMM的根底上的更加内存管理自动化的变异。ASMM是活动管理SGA,而AMM则是将SGA与PGA联合起来活动管理、调整。只需要设置memory_target一个参数就可以完成全套数据库实例内存的配置。然则那个效果没被大规模运用,因为AMM最大的题目在于不可以采纳规范大页。有时候为了利用标准大页功用,可能有点系统会禁用AMM.那么到底是用AMM依旧利用大页呢?很几个人(大师)倾向使用大页效率而非AMM,关于这些可以参见下边博文

 

MEMORY_TARGET (SGA_TARGET) or HugePages – which to
choose?

AMM and Linux Huge
Pages

Oracle Memory Management and
HugePage

 

 

何以从AMM切换来HugePage,能够参见官方文档(ID
2128928.1)

 

How
To Convert A Database Using AMM (Automatic Memory Management) To A
Database That Has Been Configured With Hugepage

 

 

参考资料:

 

http://blog.ronnyegner-consulting.de/2010/03/31/memory_target-sga_target-or-hugepages-which-to-choose/

https://docs.oracle.com/cd/E18283_01/server.112/e17110/initparams230.htm

http://www.dba-oracle.com/t_amm_automatic_memory.htm

https://docs.oracle.com/cd/B28359\_01/server.111/b28310/memory003.htm\#ADMIN11011

https://www.jianshu.com/p/9715280a4ced

http://oracle-help.com/oracle-database/relationship-memory\_target-sga\_target-pga\_aggregate\_target/

https://support.oracle.com/epmos/faces/DocumentDisplay?\_afrLoop=275836827924018&id=443746.1&\_afrWindowMode=0&\_adf.ctrl-state=149nyur949\_198

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