Your programs process PDSEs in the same manner as PDSs. To locate a member or to process the directory, several macros are provided by the operating system, and are discussed in this topic.
PDSEs are designed to automatically reuse data set storage when a member is replaced. PDSs do not reuse space automatically. If a member is deleted or replaced, the old copy of the PDS or PDSE member remains available to applications that were accessing that member's data before it was deleted or replaced.