Automatic Memory Management

Automatic Memory Management has been introduced in 11g. This enables automatic tuning of PGA and SGA with use of two new parameters named MEMORY_MAX_TARGET and MEMORY_TARGET. The Oracle Database 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).

example of changing the AMM size of the SGA and PGA:

SQL> alter system set memory_target = 400M scope=both

system altered.

SQL> alter system set memory_max_target = 400M scope=spfile;

system altered.

SQL>startup force;

To check the memory allocations in the SGA and PGA for the instance:

SQL> select component, current_size, max_size from v$memory_dynamic_components;
COMPONENT CURRENT_SIZE MAX_SIZE
---------------------------------------- ------------ ----------
shared pool 117440512 117440512
large pool 12582912 12582912
java pool 0 0
streams pool 0 0
SGA Target 159383552 159383552
DEFAULT buffer cache 0 0
KEEP buffer cache 0 0
RECYCLE buffer cache 0 0
DEFAULT 2K buffer cache 0 0
DEFAULT 4K buffer cache 0 0
DEFAULT 8K buffer cache 0 0
COMPONENT CURRENT_SIZE MAX_SIZE
---------------------------------------- ------------ ----------
DEFAULT 16K buffer cache 0 0
DEFAULT 32K buffer cache 0 0
Shared IO Pool 0 0
PGA Target 12582912 12582912
ASM Buffer Cache 25165824 25165824
16 rows selected.



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rdbms ver: 11.1.0.6
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keywords: AMM memory_target