Once you create or connect to a database within a system, Derby begins outputting information and error messages to the error log. Typically, Derby writes this information to a file called derby.log in the system directory.
Alternatively, you can have Derby send messages to a stream, using the derby.stream.error.method or derby.stream.error.field property, or to a different file, using the derby.stream.error.file property. If you use any of these properties, the property setting will appear in the log.
By default, Derby overwrites derby.log when you start the system. You can configure Derby to append to the log with the derby.infolog.append property.
For information on setting all of these properties, see the Java DB Reference Manual.