> I've heard of problems with IBExpert before - but not related to this.
>
> Usually, changing a NOT NULL flag requires everyone to log out of
> the database afterwards to take effect. Was there, by any chance, still
> some connection opened?

Restarting Firebird and recreating DB from backup have solved my
problem. I run and exit IBExpert and other FB application few times from
time when I changed NOT NULL flag, so I'm almost sure that all
connections were closed. Only almost, unfortunately...

For session run my insert, the table metadata shows field as nullable.
So it was very strange that I can't insert NULL there.

Thank you for help. Now I will know that closing all connections is
needed to made my structure updates correctly. Strange thing I haven't
seen on other RDBMS I've worked with (Oracle and MySQL)...


greetings

Sototh