15 Chapter 15. z/OS UNIX System Services z/OS UNIX System Services, which is an element of z/OS, is a UNIX operating environment. It is implemented within the z/OS operating system and is also known as z/OS UNIX. zFS can be used for all levels of the z/OS UNIX System Services hierarchy (including the root file system). zFS has higher performance characteristics than HFS, and is the strategic file system. For this reason HFS might not be supported in future releases, leading to migrating the remaining HFS file systems to zFS. The z/OS support enables two open systems interfaces on the z/OS operating system: An application program interface (API) An interactive shell interface This chapter provides information about changed and updated functions for z/OS UNIX System Services and zFS, as listed here: zFS installation changes with z/OS V1R13 zFS internal restart zFS automatic re-enablement of disabled aggregates zFS statement of direction Add symbolic links to shared root filesystem Lost message detection Provide script utility to log session Enhancements to the D OMVS,W command RACF support for z/OS UNIX user mounts Enhancements for mount and unmount processing z/OS UNIX System Services file system access IPv4 IP_PKTINFO support for AF_INET UDP sockets Option on vi to edit ASCII files © Copyright IBM Corp. 2012. All rights reserved. 283