Unprocessed Chunks

Unprocessed Chunks

Unprocessed Chunks are chunks that simply do not exist anymore. These chunks have no references in the game's memory and are stored entirely on disk until they need be accessed again. These chunks fully delete anything that passes through them and save their current NBT state. These are the chunks that you get the "Chunk still loading. You may encounter some mild performance issues." so next time you get that message when teleporting or going too fast you have those chunks to thank. These chunks also process absolutely nothing as you might expect.

Uses

The main use for these chunks is falling block duplication. When a falling block turns into a block there is still 3 tick in which the entity still exists. Because an these chunks delete the entity references we can essentially bypass the deletion mechanism allowing us to have both the entity and the block. 

A more niche use is for NBT state saving. Using these chunks we save the NBT (Named Binary Tag) of an entity just as if it was loaded from a structure block. This allows us to keep certain tags that are useful for example the minecraft:raid_configuration tag. This tag is useful because it is what makes witches throw healing/regeneration potions. This tag saving can be done by simply putting a the entity of choice into a portal. This will destroy the reference normally used to remove those tags when they aren't being used.