First of all, replace ur update your .gnowsis/config/logging.properties with the latest from SemanticDesktop/defaults/config

there we have a file-logger! this logs into .gnowsis/data/ also if the gui has died.

Then, write your log messages so that loglevel "finer" is used for real debugging whereas loglevel "fine" is for normal debug messages for developers (that are not performance taking). "Finer" is a log-level that is detailed, when the programmer's task is to debug.