Open System Services Management and Operations Guide (G06.30+, H06.08+, J06.03+)

NOTE: You cannot restore an OSS file that is larger than approximately 2 gigabytes to a system
running an RVU that does not include support for OSS large files.
Guardian Files and the pax Utility
You should not use the pax utility to back up or restore files in /G. Such files should be backed up
and restored using TMF or a version of Backup/Restore. See “Backing Up User Files” (page 186).
Unless otherwise noted, the pax utility makes no distinction between Guardian and OSS files.
CAUTION: Do not use volume-mode Guardian BACKUP or RESTORE; files can be lost or damaged
by such use if you mix Guardian and OSS files on the same disk volume. You can only back up
or restore such mixed-volume files if you do not use the volume-mode flag.
If the pax utility cannot process a specific /G file, pax returns a diagnostic message and an error
value from the underlying program interface. If possible, pax continues to process the other files.
Guardian Tape Devices and the pax Utility
The pax utility uses Guardian tape devices to read and write tape archives.
You cannot use pax on labeled tapes. If you need to backup OSS files to labeled tapes or restore
OSS files from labeled tapes, use Backup and Restore 2.0.
You are also restricted when using pax to single write operations on unlabeled tape. You can use
the pax -W norewind option only when you combine all write operations into one subshell; see
the NOTES section of the pax(1) reference page either online or in the Open System Services
Shell and Utilities Reference Manual, or see “Consolidate Changing OSS Files” (page 186).
Guardian tape devices are controlled by the Guardian tape process executing in the Guardian
environment and do not behave in the same way as UNIX devices. The interaction between the
tape process and the tape device is transparent to the pax user.
To set the block size to its maximum when using tape, specify the pax command -b28k flag.
When the pax utility accesses a tape archive, the pax utility issues a mount request to the Guardian
tape process. If you use the -W wait flag and no tape is correctly mounted on the specified drive,
the following message appears on the originating terminal:
Device not ready or tape is not mounted?
The pax utility does not proceed with reading or writing a tape until an unlabeled tape has been
correctly mounted on the specified tape drive.
If you do not use the -W wait flag and no tape is correctly mounted on the specified drive, pax
exits.
To check for outstanding requests for tape drive status, use the Guardian utility MEDIACOM. Invoke
this utility from a TACL prompt or from the OSS shell with the gtacl command. For information
about MEDIACOM, see the DSM/Tape Catalog Operator Interface (MEDIACOM) Manual.
If there are errors related to the device or to the mounted tape during the tape-mount process, one
or more of the following messages are sent to the originating terminal:
Tape is unloaded -- media is write protected
Tape mount error (Guardian file system error: n)
Tape read failed with Guardian file system error: n
Tape write failed with Guardian file system error: n
where n is a Guardian file-system error number. You can use the Guardian ERROR utility to find
the meaning of the error number. Correct the error and remount the tape or cancel the tape-mount
request using the MEDIACOM utility.
If the request is canceled or the archive cannot be opened, the pax utility issues the following
message to the originating terminal:
filename cannot be opened, Guardian file system error: n
184 Managing OSS Files