Another confusing thing about this error is that if server is open, it's using security database and one cannot attach to it with embedded to create SYSDBA.
It would be good if server detaches from security when it cannot use, so the server will not be needed to be closed to create the user with embedded. Adriano Firebird-Devel mailing list, web interface at https://lists.sourceforge.net/lists/listinfo/firebird-devel
