How to Debug Account Generator

I needed to debug workflow PAAPINVW (Project Supplier Invoice Account Generation). As per oracle documentation, it can debugged by setting profile option "Account Generator:Run in Debug Mode" to "Yes". But I could not find where debug information is being saved. So I opened the package "fnd_flex_workflow_apis" and found that debug information is being saved in a file named fdfsrvdbg.log. File is created in first directory specified by parameter 'utl_file_dir'. The file fdfsrvdbg.log is opened in APPEND mode. So in order to view only your debug information, you may delete all lines from file or move this file other dir before you start your debug.