Automatic Shared Memory Management (ASMM)

When the automatic SGA memory management feature is enabled in the database, the sizes of different components are flexible to resize to adapt to the needs of the workload without additional intervention. The database automatically distributes the SGA among the various components as required, allowing the system to maximize the consumption of all available memory.

Whenever an application needs more shared pool memory, it will obtain the extra memory from free memory in the buffer cache. Consequently, no out of memory errors are generated until the system has completely run out of memory.

When sga_target is not set or set to zero, the parameters listed above, except for shared_pool_size, behave as in previous releases of Oracle Database. The shared_pool_size will add internal overhead for metadata including data structures for processes and sessions to its value and adjust accordingly. The statistical_level has to be set to TYPICAL or ALL to use ASMM.

The following buffers are considered as manually sized components in Oracle Database 10g:  Log Buffer, Streams Pool which is new in Oracle Database 10g, other buffer caches such as RECYCLE and KEEP), fixed SGA, and internal allocations.