Shattered Kingdoms

I hear about them everytime building is involved and though I have some vague idea about what they are, could someone enlighten me?

Vnum stands for (v)irtual (num)ber. Vnums keep track of pretty much everything in the game. Each object, NPC (NPc) and room has one. This allows IMMs to reproduce objects, 'goto' rooms, spot bugs etc.

So, when an Imm says that there are not enough Vnums what does it mean? there is a fixed amount of them? Also, since everything has one assigned, if lets say someone removes an NPC from the game then there will be availability for a new room?

Every area has a certain amount of vnums assigned to it. I believe when an IMM says that there are none available, it means that the limit for that area has been reached.

Technically, if an object, NPC or room is removed from the game, the space it occupied becomes free. However, as I understand it, most aren't really removed, just recycled.

Every area has a set number of vnums allocated to it. So if a builder says he has none left, he has none left and Dulrik would need to allocate more to him.

If a NPC is taken out and rewritten to be something else there can be another NPC. Not another room or item. I think.

This is true, I keep teleporting into the old Nerina!

Having written areas for a different mud, I can tell you how it works there. Most likely it works the same way here.

Lets say the area you're building is allocated a block of 100 vnums. Your first room would have vnum 15900 for example. The last room would be 15999. That covers the 100 vnums. Your NPCs would also have the same vnums available but they would be mobnums. Your items would have the same vnums available but they would be inums.

If you eliminate a mobnum, that mobnum becomes available. If you eliminate a roomnum, that roomnum becomes available. If you eliminate an inum, that inum becomes available. They aren't interchangable.

Also, the mud where I created areas suggested using only 95 of the 100 vnums available. This would leave a bit of wiggle space for future updates but those numbers are still allocated to specific areas and are considered already used.

That's basically correct. Objects are usually the most scarce vnums, so it could explain why an imm would turn down an object request for a particular area.

As far as I understand, an entire mud also has a set number of vnums which is why things can get a little messy when it's evolved too much. No room for new areas etc.

I could be wrong, of course - I'm not exactly a code wiz.

Of course as a program the mud needs a set amount of memory to allocate but I think that is not the issue here, I think the max is close to infinite.