The VFS callable services API separates a VFS server from the logical file system (LFS) of z/OS UNIX. It is a set of protocols and callable services that deal with accessing objects in the file hierarchy.

This topic describes the services that are provided to a VFS server and the requirements and responsibilities that are placed on a VFS server.

As described in General overview, a VFS server is just one of many users of the file system. File requests that are made through the various APIs that are supported by z/OS UNIX are routed by the LFS to the PFS that owns or controls the file that is being referred to. The PFS cannot tell what kind of program originated these requests.