Lag in SL is just as you would imagine. Things happen slowly when there is lag present. Sometimes text chat can be slowed down. Sometimes frame rates will drop to very low levels making every movement appear jerky. Lag can cause your computer to freeze. It can prevent you from teleporting in or out of a region. It can prevent textures from loading and can prevent avatars from rezzing in completely. Lag is undesirable. But what causes lag and can it be prevented?
Basically, lag is a lack of speed. Your internet connection might be slow and this could cause your experience in SL to slow down. Your computer might be slow. This will manifest itself as lag through your SL viewer. This does not necessarily mean that SL is being laggy. All it means is things need to speed up on your end. On the other hand, you could have a very fast computer and very fast internet throughput yet you are still experiencing lag. This could be the SL server that your avatar is currently occupying. A good way to test this is to try teleporting to another region on another server. If you are still experiencing lag then it's probably slow throughput on your end either due to a slow (or busy) computer or too slow of an internet connection. If changing locations improves your framerates and such then there is a good chance the region you were in is experiencing lag due to the server it resides on being over taxed. In this case, restarting the sim might work. But if it's due to too many running scripts (programs) or too many avatar prims, then restarting the sim will have no effect. I mention this because I've been getting lots of requests lately to restart my sim. It's no trouble restarting it really. I just go there and Debug the land and select Restart. But more often than not, when I arrive at the sim to restart it, I am not experiencing any lag at all.
I recently ran into an ARC counter (Avatar Resource/Rendering Cost) which I have place inside my nightclub at Cherry Street. I've found that my avatar uses a great deal of resources as oposed to most. Therefore I create lag just about wherever I go. I can remove some of my huds and scripted items to bring my ARC down to an acceptable level. And I will do that should there be a great deal of lag where I'm at, but it's not always necessary. If I'm in a location where there are very few people, then it usually is not an issue. But the more avatars there are in a region, the more computations the servers need to make to keep up with them. That's when I need to lower my ARC. I'll remove my radar HUD and dance HUD and such and that usually takes care of it. But I cannot control what others do. If someone else on the sim is wearing a lot of scripted items such as HUDs or weapons or wings and piercings, etc., there's not much I can do about that except to either leave or put up with the lag.
Adjusting your 3D graphics settings can make a huge difference too. I turned my draw distance down from over 200 meters to 100 meters and it more than doubled my frame rates. Things are very smooth now even with my older 3D graphics card. Lots and lots of speed can be found by going in and customizing your graphics settings. One very important setting to look at is under your Network tab. Set the maximum throughput speed slider all the way up. Why not? I mean, why put a bottleneck in your bandwidth throughput? Just turn it all the way up so there are no restrictions to your internet speed. That right there will make a huge difference for most users.
There are multiple sources for lag, some of which were not even mentioned here. It's not always the sim you are visiting. Many times it can be the person standing next to you, using all of the server's available resources.
