sga and memory parameter

Following Value is set in my environment,i understand memory_max_target and memory value .

my question ,memory_target=sga_target+pga_target,now in this sga_max_size is 2500m which is equal to memory_max_target and memory_target parameter.

This mean SGA_max_size is fix to 2500m (mean sga size move to 2500m,if it reach to 2500m hten what will be PGA

memory_max_target      big integer  2500M

memory_target      big integer          2500M

sga_max_size                                 2500m

NAME      TYPE VALUE

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sga_target      big integer 0

SQL> show parameter pga

NAME      TYPE VALUE

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