Lou is right when it comes to the FSX
internal database, but this is not the one some of us are using.
For example, the CS FMC birds get their navdata from Navigraph and are completely independent of any FSX navdata as they relate to waypoints on a coordinate basis first, not on a named one.
So you could define a waypoint 'COOLP' by attaching some coordinates to that name, let a procedure begin there and place some constrains there too (e. g. 'supersonic only, no fat planes allowed'
) and make use of it.
That's actually how it works on most addons as they sort of share the same database through
Navigraph, which is NOT the FSX one and also not connected to it.
The only things which remain rather static are the available navaids+freqs (although you can update them and addon scenery sometimes does) and all sort of procedure data which the default FSX ATC uses and e. g. the default GPS shows.
This data does not have a central database as the information is stored in every scenery file only and may well be outdated since 2006 or so.
So if you go online or with some addon ATC, it will usually offer an option to use updated navdata too, same as on the birds you are flying if they use any kind of FMC.
With this 'world' FSX offers,
any coordinate can be assigned to
any name you like, so you can define airways, places, even virtual navaids. As long as the plane uses the same data as the ATC, they will also be able to talk and understand each other.
Looking at the above example, if the plane knows where waypoint 'COOLP' is (coordinates) but the default FSX ATC does not, this will end up in confusion.
But if the addon ATC or the online guy uses the same map as you do, he will know where you are flying to.
On the online networks there's no rule to run current data though. Those networks are designed to offer a completely free opportunity to fly.
So if you would come in with outdated navdata while the ATC may be on current one, you would declare to be unable to fly this or that procedure and ask for older ones or you would even revert back to pure vectoring.
That's no problem unless you get into very dense areas (e. g. events), where the raised workload would put too much stress on people, but the 24/7 operation can be achieved with
any navdata and charts running.
Some locations are special, they use vectoring only.
It's of course way more fun to fly current stuff and trying to keep the separation and even noise abatement thingies in place. That's the freedom of the sim, one
can do this, but does not necessarily have to.
As an example, you may fly a procedure and the ATC gives you another one or says that you should fly the published holding at VOR Charly because another pilot caused an emergency situation as he tried to land with 20 kts tailwind, because he knew better than ATC.
A current chart (or chart program) will show that holding, while not current stuff then leads to a slight moment of confusion and some extra talk necessary.
With the latest 757 4.5 update, you've all received AIRAC 1104 by the way.