version 2 protocols and the Sun NFS version 3 protocols. The remote NFS server can be z/OS, UNIX, AIX, or other systems. The z/OS NFS client is implemented on z/OS UNIX and implements the client portion of the Sun NFS version 2 protocols and the Sun NFS version 3 protocols. NFS uses the communication services provided by TCP/IP, a suite of protocols that includes the remote procedure call (RPC) and External Data Representation (XDR) protocols. RPC allows a program on one machine to start a procedure on another machine, as if the procedure were local. XDR resolves the differences in data representation of different machines. NFS, then, can be used for file sharing between platforms and file serving (as a data repository). If you are using NFS as a file server, HFS might be a better choice than using conventional MVS data sets, because of its UNIX-like features. 8.6.1 Using z/OS UNIX files The NFS server enables the client user remote access to z/OS UNIX files from a client workstation. z/OS UNIX provides a hierarchical file system (HFS) for z/OS. The HFS file system is similar to a UNIX file system. All z/OS UNIX files reside in a directory, which in turn is a file in a higher level directory. The highest level directory is called the root directory. When client users mount files from your server system, you use a common HFS prefix to distinguish z/OS UNIX files from conventional z/OS data sets. You see z/OS UNIX files in a standard UNIX format on your workstation, but the files are stored on a z/OS host system.