How to change Page Authorization Scheme on runtime in Oracle APEX

   first make select list item  P7_SECURITY_ID

that will contain all Authorization available for your APP

use this code as source 

select NAME,ID from 

APEX_200200.wwv_flow_security_schemes

 where FLOW_ID =:P7_FLOW_ID

and make process to update Page Authorization 

BEGIN

UPDATE APEX_200200.wwv_flow_steps -- PageS

SET required_role = :P7_SECURITY_ID -- Authorization schema

WHERE FLOW_ID = :P7_FLOW_ID -- APP ID

 and ID = :P7_STEP_ID  -- PAGE ID

; 

end;

--
thanks