> Well, doing the ALTER for the numeric domain is being
> executed without any error messages, so, there is - apparently -
> a difference between modifying numerics and others.

FB tries to forbid changes that would make table unreadable.
E.g. casting VARCHAR(40) to VARCHAR(20) can cause exception,
so it is forbidden.
Casting NUMERIC(4,4) to NUMERIC(4,3) will just truncate data a bit,
but will not raise exception, so it is allowed.

But the algorithm is wrong anyway - it does allow changing
NUMERIC(4,2) field to NUMERIC(4,3), which CAN corrupt the db.
(try it with value 99.99)

Ivan
http://www.volny.cz/iprenosil/interbase/