For a number of years I have been providing guidance on how to get the best performance from DNN. One of my key recommendations is to change the caching mode to "Memory" from the default setting of "File." The setting change itself is quick and harmless, simply change the value in Host Settings are you are done. Well, come to find out it isn't exactly that easy.
What Can Happen
Making this change alone is one of the best performance improvements you can get from the platform. However, as I have recently learned, it isn't quite as simple as changing the setting. In a situation with a very large client site on Azure, they were experiencing application recycles due to the file activity being created by the File caching method. We had changed the setting to Memory, however, files were still being written to the cache. Come to find out, many items had explicitly set items.
Come to find out a number of items have the cache setting explicitly configured at installation and need to be updated. The fix is as simple as running the following SQL Query. REMEMBER: backup your database before making any changes.
After you make the above change you will need to recycle the application and should see even more performance improvement than by changing the setting alone!.