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

Usage notes
Return codes
REMOUNT takes an optional argument of RDRW or READ. If you specify either
argument, the filesystem is remounted in that mode if it is not already in that
mode. If you specify REMOUNT without any arguments, the mount mode is
changed from RDWR to READ or READ to RDWR.
Note: REMOUNT is supported in a sysplex.
RESET
A reset request stops a previous UNMOUNT DRAIN request.
Note: UNMOUNT RESET is not supported in a sysplex since UNMOUNT
DRAIN is unsupported in a sysplex environment (see the description for
DRAIN).
1. The directory /samples contain sample UNMOUNT commands (called
unmountx).
2. If you unmount a TFS file system, all data stored in that file system is
discarded. For more information on TFS, see z/OS UNIX System Services
Planning.
3. If desired, the root file system can be umounted. If this is done, the IMMED
operand must be specified. Unmounting the root will force all file system activity
to be halted. Therefore, if this is done, a subsequent mount of a root file system
should be done as soon as possible.
4. While the root file system is unmounted, a ’dummy file system’ root named
SYSROOT will be displayed as the current root file system. During this time,
any operation that requires a valid file system will fail. When the new root file
system is subsequently mounted, you should terminate any currently dubbed
users or issue a chdir using a full pathname to the appropriate directory so that
the users can access the new root file system.
5. If the file system that you are unmounting is an NFS-supported file system, the
UNMOUNT command may receive an EAGAIN return code if the request was
made before an internal caching clock has expired. That is, there is a
60-second delay from last use before termination is possible. Try the request
again.
6. A file system that has file systems mounted on it cannot be unmounted. Any
children file systems must be unmounted first.
7. Currently a move of a filesystem that has open FIFOs causes all FIFOs to be
marked stale. They must be closed and re-opened. Rather than do this on a
remount, a remount attempt of a filesystem with open FIFOs will be rejected
with EINVAL, JrFIFOInFileSys. FIFOs break on move or remount because
FIFOs are always function-shipped to the filesystem owner, regardless of the
mount mode. For remount, although the owner does not change, the
vfs_umounts on all systems in the sysplex result in the XPFS control blocks
(XFS, Xnodes) being released. These blocks contain owner information.
Rejecting remount if open FIFOs is not expected to impact customers, since
remount is typically done on a READ-ONLY filesystem to switch it to RDWR,
and then back to READ, and FIFOs are not useful in a READ-ONLY filesystem.
0 Processing successful.
12 Processing unsuccessful. An error message has been issued.
UNMOUNT
Chapter 3. TSO/E commands 875