Before z/OS V1R7, the HFS file system was the primary hierarchical file system. As of z/OS V1R7, you can use any combination of HFS and zFS file systems. Because zFS has higher performance characteristics than HFS and is the strategic file system, you should replace HFS file systems with zFS file systems.

An HFS data set is a z/OS data set of HFS type, rather than VSAM or PDSE type. An HFS data set is a collection of files and directories organized in a hierarchical structure on local hard drives. Each hierarchical file system is structured like a tree, based on a root directory with various subdirectories and files. You can share HFS data sets in a sysplex.

You can access the files in a hierarchical file system by using z/OS UNIX System Services. UNIX provides a way for z/OS to access hierarchical file systems, and for UNIX applications to access z/OS data sets. You can use many of the standard BSAM, QSAM, BPAM, and VSAM interfaces to access files within a hierarchical file system. Most applications that use these access methods can access HFS data sets without reassembly or recompilation.

HFS data sets appear to the z/OS system much as a PDSE does, but the internal structure is entirely different. HFS data sets can be SMS managed or non-SMS managed. DFSMS accesses the data within the files. You can back up, recover, migrate, and recall HFS data sets.

For more information about managing HFS data sets, see z/OS DFSMSdfp Advanced Services and z/OS UNIX System Services Planning.