You can have simulated VSAM access to a UNIX file (simulated as an ESDS) by specifying PATH=pathname in the JCL DD statement, SVC 99, or TSO ALLOCATE command. For information about access using MVS access methods, see Processing UNIX Files with an Access Method.

When you use simulated VSAM, the application program sees the UNIX file as if it were an ESDS.

Because the system does not actually store UNIX files as ESDSs, the system cannot simulate all the characteristics of an ESDS. Certain macros and services have incompatibilities or restrictions when dealing with UNIX files.

Related reading: For information about VSAM interfaces and UNIX files, see Processing z/OS UNIX Files and z/OS DFSMS Macro Instructions for Data Sets.