z/OS V1R9.0 UNIX System Services Command ... - Christian Grothoff

7. Do not use the TAG parameter simultaneously with the NFS Client Xlate option.
If you do, the mount will fail.
8. The UNMOUNT keyword is not available to automounted file systems.
9. The UNMOUNT specification will only be accepted on z/OS V1R3 systems and
later.
File system recovery and TSO MOUNT
File system recovery in a shared file system environment takes into consideration
file system specifications such as AUTOMOVE | NOAUTOMOVE | UNMOUNT, and
whether or not the file system is mounted read-only or read/write.
Generally, when an owning system fails, ownership over its AUTOMOVE mounted
file systems is moved to another system and the file is usable. However, if a file
system is mounted read/write and the owning system fails, then all file system
operations for files in that file system will fail. This is because data integrity is lost
when the file system owner fails. All files should be closed (BPX1CLO) and
re-opened (BPX1OPN) when the file system is recovered. (The BPX1CLO and
BPX1OPN callable services are discussed in z/OS UNIX System Services
Programming: Assembler Callable Services Reference.)
For file systems that are mounted read-only, specific I/O operations that were in
progress at the time the file system owner failed may need to be re-attempted.
Otherwise, the file system is usable.
In some situations, even though a file system is mounted AUTOMOVE, ownership
of the file system may not be immediately moved to another system. This may
occur, for example, when a physical I/O path from another system to the volume
where the file system resides is not available. As a result, the file system becomes
unowned (the system will issue message BPXF213E when this occurs). This is true
if the file system is mounted either read/write or read-only. The file system still
exists in the file system hierarchy so that any dependent file systems that are
owned by another system are still usable.
However, all file operations for the unowned file system will fail until a new owner is
established. The shared file system support will continue to attempt recovery of
AUTOMOVE file systems on all systems in the sysplex that are enabled for shared
file system. Should a subsequent recovery attempt succeed, the file system
transitions from the unowned to the active state.
Applications using files in unowned file systems will need to close (BPX1CLO)
those files and re-open (BPX1OPN) them after the file system is recovered.
MOUNT
File systems that are mounted NOAUTOMOVE will become unowned when the file
system owner exits the sysplex. The file system will remain unowned until the
original owning system restarts or until the unowned file system is unmounted. Note
that since the file system still exists in the file system hierarchy, the file system
mount point is still in use.
An unowned file system is a mounted file system that does not have an owner. The
file system still exists in the file system hierarchy. As such, you can recover or
unmount an unowned file system.
File systems associated with a ’never move’ PFS will be unmounted during dead
system recovery. For example, TFS is a ’never move’ PFS and will be unmounted,
as well as any file systems mounted on it, when the owning system leaves the
sysplex.
Chapter 3. TSO/E commands 837