-- https://docs.oracle.com/en/database/oracle/oracle-database/23/lnpls/plsql-subprograms.html
DECLARE
  SUBTYPE License IS VARCHAR2(7) NOT NULL;
  n  License := 'DLLLDDD';

  PROCEDURE p (x License) IS
  BEGIN
    DBMS_OUTPUT.PUT_LINE(x);
  END;

BEGIN
  p('1ABC123456789');  -- Succeeds; size is not inherited
  p(NULL);             -- Raises error; NOT NULL is inherited
END;
/