Is Troubleshooting Important for you ? I hope, the answer is Yes. If that's the case for you then first thing we need to know where to look for the detailed error message when something going wrong e.g. Gateway server not pooling API configuration from Management tier, while Invoking API end user getting "Internal Server Error", "Resource not found" etc etc. There could be many types of error but often its hard to find out root cause of exact error.
Recently, I have created an API which was further calling and HTTPS endpoint. While, invoking that API I was getting error "Internal server error", However, there was nowhere I could easily locate the details error about this problem. I had looked Managed server.log, ManagedServer.out, APICS EDR file and many other files but couldn't find useful error message related to my error. Later, I found one log file "default.log" which helped me to get root cause of my error. Hence, I decided to compile a list of all logs files, their location and bit of description, so that next time when I hit the some issue, it could be much easier for me to find out root cause by looking relevant log file. This blogs definitely helps to reader as well if they got stuck with API Gateway Error.
Note: The path given in my explanation could be different than your environment but I hope you can very well workout your environment path after looking my sample PATH which I have mentioned in this blog. My base location of installation was "/u01/apics", the rest PATH should be same in your environment.
Also, before enabling debug/trace severity make sure it's impact on file size because some of the files start getting thousand of lines of logs once you enabled the debug/trace log severity.
So, here is my comprehensive logs files list, their location and bit of description which you won't find in Oracle APICS documentation.