The System Global Area (SGA) is a shared memory region that contains data and control information for one Oracle instance. An SGA and the Oracle BACKGROUND PROCESSES constitute an Oracle instance.

Oracle allocates the system global area when an instance STARTS and deallocates it when the instance shuts down. Each instance has its own system global area.

Users currently CONNECTED to an Oracle server share the data in the system global area. For optimal PERFORMANCE, the entire system global area should be as large as possible (while still fitting in real memory) to store as much data in memory as possible and minimize disk I/O.

The System Global Area (SGA) is a shared memory region that contains data and control information for one Oracle instance. An SGA and the Oracle background processes constitute an Oracle instance.

Oracle allocates the system global area when an instance starts and deallocates it when the instance shuts down. Each instance has its own system global area.

Users currently connected to an Oracle server share the data in the system global area. For optimal performance, the entire system global area should be as large as possible (while still fitting in real memory) to store as much data in memory as possible and minimize disk I/O.