Oracle 11 GB Automatic Memory Management

The 9i/10g of Oracle has gradually simplified memory management, while the 11g has gone further and introduced a new concept.Automatic Memory Management (AMM). If the DBAIf you really want to be lazy, you only need to set two parameters to give away all the troubles.
Oracle is tossing (as long as DBA). PGA
And SGATogether. The two parameters are:

MEMORY_TARGET-- Maximum memory value that Oracle can use from the operating system perspective. Dynamic ParametersMEMORY_MAX_TARGET-- Maximum value that can be set for MEMORY_TARGET. Non-dynamic adjustable.

Tip: If pfile is used and MEMORY_TARGET is set, but the value of MEMORY_MAX_TARGET is not specified, the value of MEMORY_MAX_TARGET after the instance is started is equal to MEMORY_TARGET. If MEMORY_MAX_TARGET is specified in pfile but MEMORY_TARGET is not specified, MEMORY_TARGET is 0 after the instance is started.

AMM startsMemory Manager (mman)Process.

The introduction of AMM makes Oracle memory management more flexible and diverse. There are 5 memory management forms.

• Automatic Memory Management
• Automatic shared memory management
• Manual shared memory management
• Automatic PGAManagement
• Manual PGAManagement

1) Automatic Memory Management

The default instance is AMM. As follows:

SQL> show parameters target NAME                                 TYPE                   VALUE------------------------------------ ---------------------- ------------------------------archive_lag_target                   integer                0db_flashback_retention_target        integer                1440fast_start_io_target                 integer                0fast_start_mttr_target               integer                0memory_max_target                    big integer            1216Mmemory_target                        big integer            1216Mpga_aggregate_target                 big integer            0sga_target                           big integer            0

Note that both SGA_TARGET and SGA_TARGET are 0.

2. Automatic Shared Memory Management (ASMM)

This is a management method introduced by 10 Gb. to use this method, you need to set the initialization parameter MEMORY_TARGET = 0 and then explicitly specify the value of SGA_TARGET.

SQL> alter system set sga_target=1024m scope=both;alter system set sga_target=1024m scope=both*ERROR at line 1:ORA-02097: parameter cannot be modified because specified value is invalidORA-00839: SGA_TARGET cannot be modified to the specified valueSQL> alter system set memory_target=0 scope=both;System altered.SQL> alter system set sga_target=1024m scope=both;System altered.SQL> 

The modification of these two parameters is strictly ordered. If they do not comply with the modification, it is okay-Oracle Reports an error.

3. Manual shared memory management

This is more primitive. Because it is original, the new initialization parameters SGA_TARGET and MEMORY_TARGET must be set to 0. Then, manually set the sga parameters such as ipv_pool_size and db_cache_size. Note:RESULT_CACHE_SIZEThe parameter is newly introduced at 11 GB to cache SQLResult.

4. Automatic PGAMemory Management

If AMM is usedDon't worry. If you want to achieve fine-grained control and switch to automatic PGAIn memory management mode, you need to set WORKAREA_SIZE_POLICY
= AUTO (AUTO by default), and then you need to specify the PGA_AGGREGATE_TARGET value. To precisely control PGA, WORKAREA_SIZE_POLICY = MANUAL. (Thanks vongates)

5. Manual PGAManagement

The premise is WORKAREA_SIZE_POLICY = manual, and then specify the PGA, such as SORT_AREA_SIZE, respectively.Related parameters. It is estimated that no one is doing this thankless thing now. This mode can be ignored.

AMM restrictions

If the initialization parameter LOCK_SGA = true, AMM is unavailable.

Related Dynamic View

V $ MEMORY_DYNAMIC_COMPONENTS
V $ MEMORY_RESIZE_OPS

11g simplified DBAI have made a lot of effort in my basic work. However, this also masks some technical details.
Memory Management is gradually becoming a Black Box. Of course, this is also the foundation for more stable related algorithms. In general, the advantage is greater than the disadvantage. 11g DBA,
Are you ready?

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