SGA_MAX_SIZE

Parameter type	Big integer
Syntax	SGA_MAX_SIZE = integer [K | M | G]
Default value	Initial size of SGA at startup, dependent on the sizes of different pools in the SGA, such as buffer cache, shared pool, large pool, and so on.
Parameter class	Static
Range of values	0 to operating system-dependent

SGA_MAX_SIZE specifies the maximum size of SGA for the lifetime of the instance.