> I have debugged this following procedure call using this procedure:
>
> CREATE PROCEDURE ADD_NUMBERS (NUM1 INTEGER, NUM2 INTEGER) RETURNS (RES
> INTEGER)
> AS BEGIN
> RES = NUM1 + NUM2;
> END
>
> And this CallableStatement:
> {CALL ADD_NUMBERS(?, ?, ?)}

You have forgotten CallableStatement.registerOutParam(int, int) call as I
suggested in my private email.

> When debugging, I can tell that
> {CALL ADD_NUMBERS(?, ?, ?)}
> gets converted to
> EXECUTE PROCEDURE ADD_NUMBERS(?, ?, ?)
>
> I'm guessing the conversion to native procedure call is the problem?

Unless you mark some params as out all they are treated as in.

Roman