> You are right, when modified security2.fdb to allow adding new users, then it's a feature I have created.
>
> My user to add and delete users is the ADMINISTRATOR. So I have added the following grant to the security2.fdb by moving it from
> the firebird root directory and moving it back afterwards:
>
> GRANT SELECT, INSERT, UPDATE, DELETE, REFERENCES ON USERS TO ADMINISTRATOR;
>
> But why does the security service block the access only in one direction.

Just look at view USERS in security database ...

Ivan