Hi @Kel3, let me see if I can help out here.
As @uliwooly mentioned, I assume that you are referring to the cache memory? In previous version of Android, there was a feature enabling you to clear cache for all apps. This feature was removed back in Android 8, so if you want to clear cache on your XZ2, you will need to do it for one app at a time. To clear cache for an app, find and tap Settings > Apps & notifications > Show all XX apps > App name > Storage > Clear cache.
I hope that helped, let me know if you have any further questions!
