In this technical report, we develop a framework for the analysis of resource usage in concurrent systems. We propose an oracle - the omniscient garbage collector (OGC) - that decides precisely the minimal resource consumption of a process: its resource index. The underlying theory is developed as a nominal automata framework, and applied to the specific problem of tracking resource usage. The framework is put into practice to track resource usage and consumption in pi-calculus processes. Two complementary abstractions are proposed: the first is based on the labelled transitions, while the second relies on a variant calculus - slice-pi - that enrich reductions with observations about the resource events. The two abstractions are tested experimentally on classical pi-calculus examples using a prototype analysis tool. In all the examples the resource index can be computed very quickly although in theory it is an NP-complete problem.