Problem description:I am always in the process of trying to make things run as smoothly as possible, and this is something I don't quite understand 100% of the way. I am not sure from what I have read, exactly what happens when you have different dmm files with different maxx, and maxy.

From what I understand, the world itself has one maxx, and one maxy and they are both set to whatever the highest maxx and maxy are, out of every dmm file you include when you compile. I am guessing this would make every z level you have have the x y dimensions of the world's maxx, and maxy.

I'm debating if I should just make every dmm file all have the same maxx and maxy, and just work around it, and situate everything accordingly. What I really want to know before I go through the trouble of doing this, how are the empty areas on a z level handled in memory

Are they all turned into turf that take up memory, or does a dmm file with smaller maxx, and maxy somehow not generate a turf for every tile with in the dimensions of the world's maxx and maxy. I'm sorry if this seems like just a pestering about useless technical info, but I just want to know, and for everyone else reading to know, how much, if at all, these things matter

The map is indeed compiled into a single file with the size of the largest z-layer of the bunch. The empty space is filled with the value of world/turf which is /turf by default.

If you need to have maps of varied sizes the most accepted method of doing so is to have them all a single size then surround the edges of the smaller maps with some kind of border. You can fill the extra space around them with other maps so there's as little waste as possible.
Thank you for the advice, it has really helped. Now that I have done a bunch of map modification, I realized I had to make the inside of caves a bunch of different times, for the same cave, because each one is assigned to a different area, but only one is ever used, depending on which area the savefile says the cave is in.

The bad thing about this is that some of them are big, but right now it seems like the only way to do it. I never actually change the area the cave is in, but I change the destination of the cave entrance, based on who is using the cave.

This is probably the worst way I could do things, but also it seems like it is the only way to easily have this be area based. The reason I keep it area based, is when I create the savefile I just save everything a player has dropped in the cave area into one savefile. It saves and loads fast and with no glitches. The problem is the number of times I have the inside of each cave on the map, each one with a different area. It is taking up a huge amount of space.

The reason I do this this way with different areas is there are different areas for players that are considered safe, and those that are considered different types of criminals or not safe for different reasons. It makes saving and loading so much easier this way, because I can just save every movable object in the area.

I thought about this, and its so tempting to just change the area of the turfs in the cave as needed while the game is running, so I only need to put the inside of each cave on the map once. I'm sorry guys, I know I'm being a bit difficult even suggesting this again.