Technical data

Using BACKUP
11.5 Understanding Save Sets
11.5.4 Sequential-Disk Save Sets
Sequential-disk save sets allow you to treat a Files–11 disk volume sequentially,
(like a magnetic tape volume). The primary advantage of using sequential-disk
save sets is that you can mount multivolume save sets one volume at a time.
This is particularly useful on systems without tape drives that have a large
fixed-media disk and a small removable disk.
When one sequential disk is full, BACKUP prompts you to mount another disk.
You can use more than one disk device at a time to save or restore data; this
allows processing to continue on another disk while the one most recently used is
spinning down.
You must have the privilege LOG_IO or PHY_IO to read or write a multivolume
sequential-disk save set.
Before creating a sequential-disk save set, mount the first volume of the
sequential-disk save set using the DCL command MOUNT/FOREIGN. Although
the disk is mounted with the /FOREIGN qualifier, BACKUP manages the disk
using Files–11 structure.
When you perform a save operation to a sequential disk, you must use the output
save-set qualifier /SAVE_SET. When you perform a restore operation from a
sequential disk, you must specify the input save-set qualifier /SAVE_SET. If you
do not specify the /SAVE_SET qualifier, BACKUP displays the following error
message:
%BACKUP-F-IMGFILSPE, /IMAGE specification must only have device name
Do not specify a directory name for the save set; sequential-disk save sets are
always entered in the master file directory [000000]. Even if you specify a
directory other than the master file directory in a save operation, the save set
is entered in the master file directory. If you specify a directory other than the
master file directory in a restore or list operation, BACKUP returns an error
message indicating that it cannot locate the file.
BACKUP does not initialize the first sequential-disk volume because the default
is /NOINITIALIZE; however, continuation volumes are initialized. Unless you
specify the command qualifier /INITIALIZE, the following restrictions apply to
the first sequential-disk volume:
• The disk must be Files–11 Structure Level 2 or 5.
• The disk must not be part of a volume set.
• The cluster factor of the disk must be 1.
• The free space on the disk cannot be fragmented into more than 100
contiguous extents.
• The index file cannot be extended.
• The master file directory cannot be extended.
Volumes you use for sequential-disk save sets should contain only save sets. You
must initialize a volume that has been used for general file processing before
using it as a sequential-disk volume. You can place a maximum of 12 save sets on
a single sequential disk. Use Files–11 disk save sets if you want to create more
than 12 save sets on a single disk.
Using BACKUP 11–9