By convention sources whos name begins with an underscore are considered hidden. Hidden sources interact with the server like normal but some sources may choose to not to display the data to the client.
Hidden Channels in RDV for example are not displayed by default and have to be shown by selecting View -> Show Hidden Channels in the menu.
The _Metrics channels give information about the state of the DataTurbine Server
The Available Channels:
In particular watch MemoryUsed, TotalMemory, and SocketRate. The first two will let you see when Java garbage collection events occur which are often a big culprit for unexpected system load. The latter will give you feedback about overall client activity. E.g. with no sinks active you will see the baseline data flow for your sources. Beware of a Heisenberg-like uncertainty principle; the act of fetching _Metrics to look at them will change the _Metrics. Also beware sinks that seem inactive but may actually be status polling etc.
Keeps a log of the sources and sinks that connect to a DataTurbine server. These can be a great tool for debugging interactions between servers sources and sinks. A separate channel is created for each source and sink the connects to it, as well as the server itself. The channels have the same name as the source itself