V$SGA ---- Displays summary information about the system global area (SGA).
 

V$SGAINFO ---- Displays size information about the SGA, including the sizes of different SGA components, the granule size, and free memory.
 

V$SGASTAT ---- Displays detailed information about the SGA.
 

V$SGA_DYNAMIC_COMPONENTS --- Displays information about the dynamic SGA components. This view summarizes information based on all completed SGA resize operations since instance startup.
 

V$SGA_DYNAMIC_FREE_MEMORY -----Displays information about the amount of SGA memory available for future dynamic SGA resize operations.
 

V$SGA_RESIZE_OPS ---- Displays information about the last 400 completed SGA resize operations.
 

V$SGA_CURRENT_RESIZE_OPS --- Displays information about SGA resize operations that are currently in progress. A resize operation is an enlargement or reduction of a dynamic SGA component.