Updating entities when loading the world.

I have entities that use cyclic procedures, so that they are interrupted when the world is unloaded, so I want to start them again as soon as the world is loaded again. Using a "Player joins the world" trigger has a certain radius, but I need each uploaded entity(I'm also sure it will cause problems in multiplayer.). I also couldn't use "Minecraft loads a world" trigger, couldn't find a way to run an iterator for entities(the coordinates for the start are needed there, but this trigger does not support them).

So, does anyone know a way to get each entity when loading the world?