This section applies to file systems that are non-sysplex aware (see Figure 1).

Figure 1. Non-sysplex aware file system (read/write)

When a file system is mounted read/write (for example, on SY2), the mount request is sent to the local physical file system (in this case, zFS) and zFS opens the file system data set (for read/write). If the mount is successful on that system, z/OS® UNIX sends a signal to the other sysplex member systems to issue a catch-up mount on each system. Each z/OS UNIX on each other system then reads the CDS and determines that it needs to record that the file system is mounted read/write and that SY2 is the owning system. The local zFS on the other systems does not receive a local mount request. The mount on SY2 is “logically” mounted on each of the other systems.

For read/write mounted file systems, file requests are function shipped to the owning system. The owning system is the only system where the file system is locally mounted and the only system that does I/O to the file system. File requests from systems other than the owning system have a longer pathlength through XCF communications. Read/write mounted file systems are referred to as being non-sysplex aware.