Yellowfin has a number of different logging facilities for different parts of the application. In a standard installation, these are located in the directory:
Yellowfin/appserver/logs/

The main Yellowfin application log is named yellowfin.log, and contains error and warning messages, and information about what Yellowfin is doing. This can be useful to help diagnose problems. In some cases a finer level of detail is helpful. Yellowfin can be configured to log additional debugging information to this file. To do this, find the file log4j.properties, located at:
Yellowfin/appserver/webapps/ROOT/WEB-INF/log4j.properties

Towards the bottom of the file, find the line:
[quote]log4j.category.com.hof=INFO[/quote]
Change this to:
[quote]log4j.category.com.hof=DEBUG[/quote]

Save this file and restart Yellowfin. Debugging information will now be logged to yellowfin.log, along with all the information that was previously logged.

Generally you will not need to do this unless directed to do so by Yellowfin support. With debug logging turned on these log files will grow quite quickly, especially on a system with a large number of users. After you are finished debugging your problem, it is best to set the log level back to INFO in log4j.properties.