Logically, a PDSE directory looks the same as a PDS directory. It consists of a series of directory records in a block. Physically, it is a set of pages at the front of the data set, plus additional pages interleaved with member pages. Five directory pages are initially created at the same time as the data set. New directory pages are added, interleaved with the member pages, as new directory entries are required. A PDSE always occupies at least five pages of storage.