create domain d1 as char(10) character set none;

create table t1(s d1);

insert into t1(s) values ('абвгд');

commit;

select * from t1

alter domain d1 type char(10) character set utf8;

insert into t1(s) values ('абвгдежзик');

commit;

select * from t1

alter domain d1 type char(10) character set none;

select * from t1

Arithmetic overflow or division by zero has occurred.
arithmetic exception, numeric overflow, or string truncation.
string right truncation.
expected length 10, actual 40.

create domain d2 as char(40);

alter domain d2 type char(10);