The z/OS® Distributed File Service z/OS File System (zFS) is a z/OS UNIX System Services (z/OS UNIX) file system that can be used in addition to the hierarchical file system (HFS). zFS file systems contain files and directories that can be accessed with z/OS UNIX application programming interfaces (APIs). These file systems can support access control lists (ACLs). zFS file systems can be mounted into the z/OS UNIX hierarchy along with other local (or remote) file system types (for example, HFS, TFS, AUTOMNT, and NFS). For more information about ACLs, see z/OS UNIX System Services Planning.

zFS can be used for all levels of the z/OS UNIX System Services hierarchy (including the root file system). Because zFS has higher performance characteristics than HFS and is the strategic file system, HFS might not be supported in any future releases, which will cause you to migrate the remaining HFS file systems to zFS.

zFS can run sysplex-aware for read/write mounted file systems and for read-only mounted file systems. For more information, see Specifying zFS file systems as sysplex-aware, Terminology and concepts, and Using zFS in a shared file system environment.

Beginning with z/OS V1R13, zFS has enhanced its sysplex-aware support. For many file operations, zFS can now directly access zFS read/write mounted file systems in a shared file system environment from zFS client systems. In z/OS V1R13 and later releases, when zFS runs in a shared file system environment, zFS always runs sysplex-aware on a file system basis (sysplex=filesys). See zFS enhanced sysplex-aware support for more information.

zFS and HFS can both participate in a shared sysplex. However, only zFS supports security labels. Therefore, in a multilevel-secure environment, you must use zFS file systems instead of HFS file systems. See z/OS Planning for Multilevel Security and the Common Criteria for more information about multilevel security and migrating your HFS version root to a zFS version root with security labels.