Automatic and Manually sized Components of SGA

The parameter SGA_TARGET specifies the total size of all SGA components. If SGA_TARGET is set to a value greater than zero then
DB_CACHE_SIZE,
SHARED_POOL_SIZE,
LARGE_POOL_SIZE and
JAVA_POOL_SIZE are automatically sized.
are automatic sized components.

On the other hand,
LOG_BUFFER,
BUFFER_POOL_KEEP,
BUFFER_POOL_RECYCLE,
DB_nK_CACHE_SIZE other than DB_CACHE_SIZE,
STREAMS_POOL_SIZE ,
Fixed SGA and
other internal components are manually sized components.

However setting the value to manually sized components automatically reduce the value from SGA_TARGET if SGA_TARGET is set to value greater than zero.

When SGA_TARGET>0 then automatic sized components of SGA are automatically allocated and this is called Automatic Shared Memory Management.

Both the automatic and manually sized components of SGA are dynamic components because they dynamically can be changed. You can see them from V$SGA_DYNAMIC_COMPONENTS.