Only on office time you can perform update, delete and insert operation - DBMS (Trigger)

create or replace trigger t3 before delete or insert or update on empmaster

begin

if(to_char(sysdate,'day')IN('saturday','sunday'))OR(to_char(sysdate,'hh:mm')NOT BETWEEN '8:30' AND '18:30')

then

raise_application_error(-20001,'Table is secured');

end if;

end;