IBM IP stack required for MVS Sequential, MVS GDG, and MVS PD

The FTP Heuristic methods used to interface with MVS Sequential, MVS GDG, and MVS PDS, are designed for FTP servers (at the mainframe) that use the IBM IP stack. Therefore, when you use FTP with an MVS Sequential, MVS GDG, or MVS PDS file system on a mainframe computer, you need to make sure that the FTP server is using an IBM IP stack. If any other IP stack is in place, the FTP heuristics feature will not work or may require modification.