Understanding Multivolume BACKUP Operations

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HP OpenVMS System Manager's Manual, Volume 1:...

Using BACKUP

Listing the Contents of a BACKUP Save Set

Understanding BACKUP Tape Label Processing

Understanding Multivolume BACKUP Operations

When you save data with BACKUP, the save set often spans more than one volume, creating a multivolume save set. When this occurs, BACKUP fits as much data as it can on the first volume, then dismounts it. Depending on whether you specified more than one drive in the BACKUP command line or if you are using a tape loader, BACKUP then performs the following actions:

If you specified only one drive in the BACKUP command line and you are not using a tape loader or operator assistance, BACKUP prompts you to remove the tape that is in the drive and insert another one:

%BACKUP-I-RESUME, resuming operation on volume 2
%BACKUP-I-READYWRITE, mount volume DAILY02 on MUA0: for writing
Respond with YES when ready:

If you are using OPCOM and the /ASSIST qualifier (the default), the following message appears on your terminal screen:

%BACKUP-I-RESUME, resuming operation on volume 2
%MOUNT-I-OPRQST, Please mount volume DAILY02 in device MUA0:
BACKUP requests: Saveset DAILY.SAV, Volume number 02, write ENABLED

After you insert and load the second volume (or an operator fulfills the mount request), BACKUP continues writing data to the second volume.

If you specified multiple drives on the command line, BACKUP continues writing data to the second volume, assuming the drive is loaded, is on line, and has the correct volume label. BACKUP unloads the first volume and displays the following message:
```
%BACKUP-I-RESUME, resuming operation on volume 2
```

If you are using a tape loader, BACKUP continues writing data to the tape in the next slot, assuming the tape loader has an adequate supply of correctly labeled tapes. BACKUP rewinds and unloads the first tape and displays the following message:
```
%BACKUP-I-RESUME, resuming operation on volume 2
.
.
.
```

Multivolume Tape Labeling

In a multivolume save-set operation, BACKUP does not initialize the first volume (unless you use the /REWIND qualifier). BACKUP does initialize subsequent volumes. BACKUP determines the volume labels for subsequent volumes as follows:

If you did not specify a label on the command line, BACKUP uses the first six characters of the save-set name to create a label for the first volume (unless you use the /EXACT_ORDER qualifier, in which case BACKUP preserves the volume label on the tape). For subsequent volumes, BACKUP uses the first four characters from the label of the first volume plus the number of the volume in the sequence. For example, suppose you are saving files that require three tapes and the save-set name is BACKUP. If you do not specify a label, the first tape is labeled BACKUP, the second BACK02, and the third BACK03.

If you specified a single label on the command line using the /LABEL qualifier and it matches the label of the first volume, BACKUP labels subsequent volumes with the first four characters of the label from the first volume plus the number of the volume in the sequence. For example, suppose you are saving files that require three tapes and the first tape is labeled TAPE. The second tape gets the label TAPE02, and the third tape gets the label TAPE03.

If you specified multiple labels on the command line using the /LABEL qualifier (without the /EXACT_ORDER qualifier), BACKUP uses the labels you specify. If the operation requires more labels than you specified, BACKUP uses the first four characters of the last volume label and the volume number of the tape.

You can use the /EXACT_ORDER qualifier in conjunction with the /LABEL qualifier to specify the order in which you want BACKUP to use the labels. BACKUP continues the operation as long as the label of the tape in the drive matches the corresponding label on the command line. If you do not specify enough labels on the command line to complete the operation, BACKUP prompts you to enter a label for the tape in the drive.

As a safeguard against initializing or writing the wrong tape, BACKUP compares the label that you specify on the command line to the label of the tape in the drive. Understanding BACKUP Tape Label Processing describes how BACKUP processes tape labels and handles a label mismatch.

MOUNT Messages When Backing Up Tapes

The MOUNT utility generates VOLINV messages on continuation tape volumes during backups when you use devices that have loaders or when the stackers or loaders become empty. The following example shows messages displayed:

%MOUNT-I-MOUNTED, ABCD03 mounted on _$4$MUA3: (HSC70)
%BACKUP-I-RESUME, resuming operation on volume 4
%MOUNT-F-VOLINV, volume is not software enabled
%BACKUP-I-READYWRITE, mount volume 4 on _$4$MUA3: for writing
Enter "YES" when ready: yes
%MOUNT-I-MOUNTED, ABCD04 mounted on _$4$MUA3: (HSC70)

Once the devices are put back on line or the media is made ready, the backup session continues or finishes as expected. This problem will be addressed in a future release.

Listing the Contents of a BACKUP Save Set

Understanding BACKUP Tape Label Processing