This command is not encapsulated. It runs only on the process in which it's invoked. Since data source managemnent and data distribution are all done in the MPI_ROOT_RANK and that runs the interactive interpreter as well, this is normally fine. Note that if SpecTcl is taking data from an online data source, stopping without detaching (usually done by attaching to the file /def/null), will eventually, most likely cause data taking to stall or ring items you might care about to be dropped depending on the options passed to ringselector