To be accessed from the Z Data Tools panels, a named library must exist. To expand on this: suppose a library data set name is entered in an LMS-related Z Data Tools panel field (for example, the Copybook or Template Data set name field on the edit entry panel). A PDS or PDSE data set of the given name must exist. Z Data Tools checks this prior to calling the user exit. Therefore the exit cannot support user defined, logical names which would otherwise be translated by the exit.