Minecraft wiki entry for Block_and_item_duplication, associated text: When you overflow chunk memory, you will be able to freeze chunk. What this means is that changes on this chunk will not be saved and after loading it again it will return to the previous state. The best way to do this is to create books filled with about fifty pages of random Unicode characters and put it in a chest. There are mods for doing this automatically, but you can also do it manually by copying and pasting. You will need two different types of books for this to work.