Statement failed, SQLCODE = -902 Error reading data from the connection.
This error shows up when you lost connection to the Firebird server. Common causes are:
a) someone rebooted or restarted the server
b) Firebird server crashed
If this shows up repeatedly with some particular query, try with latest Firebird version. If the problem still occurs, contact the developers, as it it most probably a bug in Firebird.
Please note that other instances of Firebird server are available when one of them crashes. If you are using the SuperServer, the entire server would crash, but it would be restarted automatically (either by the Firebird Guardian or by the system if you run it as a system service under Windows). If you use Classic, only one instance would crash, while others would keep running.
In both cases, Firebird server is available for subsequent connections, so this may trick you into thinking that server did not crash.