About application setting debug
Access Gateway applications include a debug setting, which can be used with header, policy, and other application types to display additional information useful for troubleshooting. When set, Access Gateway generates additional information about headers, sessions, policy, and more.
During implementation and testing, Access Gateway apps can be spoofed to behave like a sample policy or header application. See Configure applications for testing.

Setting an application to debug overrides the system level log verbosity setting, elevating the system level log verbosity to Debug. This can cause rapid consumption of disk space. Only specify application Debug mode while testing and debugging applications and disable immediately when testing is complete.