Blue Meanies of Region LagCompared to private Estate owners, Mainlanders have fewer tools for finding sources of lag in their regions. In particular, we lack a "Top Scripts" list of objects that may contribute to sim-side lag. But even very busy scripts mostly lag other scripts. "Mostly." And there's a tool that can help identify one way scripts *can* hurt performance -- including viewer-side lag.
That's lag contributor is frequent object updates, which must be sent directly from the sim (no help from a Content Delivery Network) and received and processed by each viewer showing the updating object. This can be a particular burden on metered or low bandwidth connections. And then the viewer needs to draw each update, which can be a problem for complicated objects viewed on less powerful computers.
Fortunately, there's an easy, built-in way to find objects generating lots of object updates: Turn on "Develop" / "Show Info" / "Show Updates to Objects" and pan around your environment. (If you don't have a "Develop" menu bar item, turn it on in "Preferences" /"Advanced".) If you see something spewing a steady stream of blue squares skyward, that object needs closer inspection, and may even warrant removal if your situation is particularly vulnerable to network or viewer lag.
You'll probably see some individual red squares stream upward as you pan around. If they don't repeat, they can be ignored -- they've just come into view. (If they *do* repeat, especially accompanied by green squares indicating object deletion, they may be something temp-rezzing, which is another potential source of lag.)
This tool is also useful for determining which object updates are actually being processed by the viewer. Note that objects continue to get updates even when they themselves are hidden behind other surfaces, although that may not incur the same rendering cost as drawing updates to a visible object.
It's always a judgment call whether a frequently updating object is worth keeping despite whatever load it puts on the network and viewer. One of the charms of Second Life is the dynamic environment -- and we'll be seeing more of that with one of the Lab's upcoming projects, "Animesh" -- so don't throw out all your animated objects. Rather, just be aware of which objects are sending updates, try to understand why, and maybe assess whether they're worth the load.