Automatic Tuning of Memory Management

4.2.2 Automatic Tuning of Memory Management

Two memory management initialization parameters, MEMORY_TARGET and MEMORY_MAX_TARGET, enable automatic management of the System Global Area (SGA), Program Global Area (PGA), and other memory required to run Oracle Database.

MEMORY_MAX_TARGET specifies the maximum value to which MEMORY_TARGET can grow dynamically.

Table 4-2 MEMORY_MAX_TARGET and MEMORY_TARGET

if ...	And ...	Then ...
You omit MEMORY_MAX_TARGET	You omit MEMORY_TARGET	The initialization parameters are left at their default values (0) and Oracle Database does not automatically tune memory
You omit MEMORY_MAX_TARGET	Include a value for MEMORY_TARGET	The database automatically sets MEMORY_MAX_TARGET to the value of MEMORY_TARGET
You omit MEMORY_TARGET	Include a value for MEMORY_MAX_TARGET	The MEMORY_TARGET parameter defaults to zero

Oracle Database uses a noncentralized policy to free and acquire memory in each subcomponent of the SGA and the PGA. Oracle Database automatically tunes memory by prompting the operating system to transfer granules of memory from less needy to more needy components. The granularity of the memory transfer is dependent on the current free memory and the amount of memory the operating system requires to maintain a basic level of service.

http://docs.oracle.com/cd/E25178_01/server.1111/e17157/planned.htm#HAOVW11874