Figured out the cause, but still short for solution.
.
I have been using I.Prenosil enhanced isc4 gdb, where USERS table has been replaced with USERS2.

CREATE TABLE USERS2 (
USER_NAME USER_NAME,
SYS_USER_NAME USER_NAME,
GROUP_NAME USER_NAME,
UID UID,
GID GID,
PASSWD PASSWD,
PRIVILEGE PRIVILEGE,
COMMENT COMMENT,
FIRST_NAME NAME_PART,
MIDDLE_NAME NAME_PART,
LAST_NAME NAME_PART,
FULL_NAME COMPUTED BY (first_name || _UNICODE_FSS ' ' || middle_name || _UNICODE_FSS ' ' || last_name )
);

CREATE VIEW USERS(USER_NAME,SYS_USER_NAME,GROUP_NAME,UID,GID,PASSWD,PRIVILEGE,COMMENT,FIRST_NAME,MIDDLE_NAME,LAST_NAME,FULL_NAME)
AS

SELECT *
FROM users2
WHERE EXISTS (SELECT * FROM log_proc(users2.user_name))


When I open USERS2 table (or USERS view) with IBAdmin, I can enter accented characters into FIRST_NAME and LAST_NAME.
When I do the same with isc_add_user, I get the 335544754 error.

Does isc_add_user check the strings before it enters them into database or what?

Riho-Rene Ellermaa
senior programmer
Hansabank