Your computer has two places that it stores data for the applications that it runs. One is the RAM and one is the hard drive. The Hard drive serves as the giant database of everything that you have on your computer. All of your files, documents, applications, system files etc. The RAM is where your computer stores data and information for processes, applications, documents etc for whatever is currently running.
In this way you can compare the hard drive to a filing cabinet below the desk in an office with everything crammed into a small space. Thinking like that also means that RAM would be like the workspace on top of your desk. Everything that your office has is stored in the filing cabinet, and when you want to use something you take it out of the filing cabinet and put it on your desk for faster access. This is like how a computer works.
You know how it sometimes takes ages for a program to load? What the computer is doing in this time is taking the data from the hard drive and putting it all onto the RAM so it can access the data faster when you’re using your application. If the computer didn’t have RAM then everything would be INCREDIBLY slow, because every time you wanted to do something within the program you’re running, it would have to reference whatever you’re doing from the hard drive which is incredibly slow. This is why it offloads data from the hard drive to the RAM. RAM is virtually instantly accessible memory, so when you’re running a program and doing things with it, RAM enables data to be read and processed very fast.
RAM runs at the same speed no matter how much memory is stored on it, which is why having more RAM does not mean that your computer will run faster. 4Gb of RAM is very suitable, any more RAM than that is usually only for either professionals who use really high-end applications that require a lot of ‘workspace,’ or gamers and people that like to run stuff like Crysis, oblivion, traktor, ableton, Itunes, 200 tabs in chrome, and whatever other shit all at the same time. Having more RAM in that case would allow them to do more stuff at the same time although it would put in incredible strain on the CPU.
When you’re running traktor there is actually a RAM meter. I have a shitty computer and mine is always low anyway. RAM storage on any decent computer tends to fluctuate between 0.5 and 2.5Gb of stored data if you use it heavily, at least that’s what I noticed back in my gamer days. You should technically always be in the safe zone. You only need more RAM if your computer RAM meter ever needs to go over it’s limits, which I can’t imagine any DJ ever needing. I’m on a 2Gb system right now and never seen it get even near half way in Traktor.
If you want your computer to be faster, your best bet is to upgrade the CPU, because it’s the primary link between all the other components in your computer. Lagging isn’t usually a problem with speed of accessing the data the computer needs (RAM), more often it’s the speed of processing of that data that slows your computer and that’s your CPU’s fault. If you want stuff to load faster, the hard drive needs to be faster, if you’re running really high-end applications in a professional environment or super-high-spec video games and want them to run smoother and you’re a freak about computer perfomance, then you can get faster RAM but the main culprit of lagging is usually just the CPU.
As amidoinitrite said, it’s quite an accomplishment to use over 4Gb of RAM. You won’t ever need more than 4Gb for Traktor. Just get a faster CPU if it’s slowing you down.