variable declared outside subprogram or process must be shared variable

variable set_10_external : STD_LOGIC;

declaration error, variable declared outside subprogram or process must be shared variable

already declared a variable, got error, isn't it shared variable

architecture syn of Transmit2 is
variable set_10_external : STD_LOGIC;
begin
	H1:tether2 port map ( 
					
				set_10	=> set_10_external, --: IN STD_LOGIC;
...