If you moved to BI Publisher 11g or OBIEE 11g from BI Publisher 10g, you would have realized that debug option is no more part of BI Publisher Administration UI. In 10g we can set the debug log level from Administration UI under Server configuration section but in 11g no more.
In OBIEE 11g, it is central logging process which is part of Fusion Middleware. One can set the log level and view the log from Oracle EEnterprise Manager.
Use the same userid /password as set during OBIEE installation or you use to access WLS console
From the left pane expend the Application Deployment node and click the “bipublisher application. This will open the BI Publisher deployment details page on right side of the pane.
Click on the Application Deployment and select the Log from the drop down list
There are two options..
1) Log Configuration: This allow to set the log level for speciifc component. If we just want to debug the BI Publisher specific funcitonality, expand the Root Logger => oracle node and select the oracle.xdo node and set the desires log level. Trace 32 (FINEST) is the lowest level of logging and it may log many information which may not useful for day to day development or troubleshooting.
2) View Log Messages: The other option within the Log pane for review the log.
The log file can be exported to different format or can be queried based on the Message Type or ID. Explore the logging feature and get use to this functionality.
Hope this help in your BI Publisher/OBIEE development process.