System Global Area
Oracle's shared memory region containing structures such as the buffer cache, shared pool, redo log buffer, and other instance-wide components.
Oracle Runtime Context
The System Global Area is shared Oracle instance memory containing structures such as the database buffer cache, shared pool, and redo log buffer. SGA sizing should reflect the workload's parse behavior, block reuse, and redo characteristics rather than one universal cache-ratio target.
Memory Boundary
SGA is distinct from process-private PGA memory. Operating-system page behavior and NUMA placement can also influence the physical performance of a large shared-memory region.