This document is the User Manual for the decision support software IRIS - Interactive Robustness analysis and parameters' Inference for multicriteria Sorting problems (Version 2). This tool has been built to support the assignment of actions (alternatives, projects, candidates) described by their evaluation (performance) at multiple dimensions (criteria) to a set of predefined ordered categories, using a pessimistic concordance-only variant of the ELECTRE TRI method. Rather than demanding precise values for the ELECTRE TRI parameters, IRIS allows to enter constraints on these values, namely assignment examples that it tries to restore. It adds a module to identify the source of inconsistency among the constraints when it is not possible to respect all of them at the same time. On the other hand, if the constraints are compatible with multiple assignments for the actions, IRIS allows to draw robust conclusions by indicating the range of assignments (for each action) that do not contradict any constraint