This is the relative name (RN) -- just the final path segment -- that this SAS-expander hardware definition contributes to its own distinguished name. UCS Manager builds the full DN by appending an object's RN onto its parent's DN, so this value is the piece that uniquely distinguishes this instance from any siblings registered under the same parent. A typical RN here is a short token such as 'sas-expander-def-1', distinct from the RN any sibling SAS-expander hardware definition would use at the same level of the tree.