Anonymous: I don't know what they are. I assume they're timezone data, but it seems wasteful to have them all loaded all the time. Markus: I'm sure there's some combination of queries and filters and whatnot that could probably do that, or else the data could be processed in another way. JRuby's strings are all just byte in the end, so it would be a matter of writing scripts/code/filters that can check if the byte contents are equivalent. The other option would be using one of the tools that work against the *live* heap to do that inspection via the debugging interfaces. But there's definitely a way.