Understanding Save Sets

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

Using BACKUP

Understanding the Backup Interfaces

Understanding BACKUP File Formats

Understanding Save Sets

When you enter a BACKUP command to save files to a tape, BACKUP writes the files to a special file called a save set. You can also create a save set on a disk using the /SAVE_SET qualifier. Save sets are classified according to the media on which they reside. Save-Set Types lists the types of media that you write a save set to.

Table 3 Save-Set Types
Media Type For More Information

Magnetic tape
Magnetic Tape Save Sets

Files-11 disk
Files-11 Disk Save Sets

Files-11 disk on a remote node (network save set)
Network Save Sets

Sequential disk
Sequential-Disk Save Sets

**Table 3** **Save-Set Types**
Media Type	For More Information
Magnetic tape	Magnetic Tape Save Sets
Files-11 disk	Files-11 Disk Save Sets
Files-11 disk on a remote node (network save set)	Network Save Sets
Sequential disk	Sequential-Disk Save Sets

Magnetic Tape Save Sets

Magnetic tape is the most commonly used media for storing BACKUP save sets. It is less expensive than disk media, and its compact size makes it easy to store. You can use more than one tape device at a time to save or restore data; this allows processing to continue on another tape while the one most recently used is rewinding.

BACKUP treats all magnetic tape files as BACKUP save sets. Because you cannot use save-set specifications as both the input and output specifiers in a BACKUP command line, you cannot perform a BACKUP operation from one magnetic tape to another.

HP recommends that you copy magnetic tape save sets to disk with the BACKUP command; however, you can use the DCL command COPY on magnetic tape save sets that were created with the /INTERCHANGE qualifier.

Save-set specifications on magnetic tape are limited to 17 characters, including the period delimiter (.) and file type. The following text is a valid save-set specification:WKLY27JAN2002.BCK

When restoring data from tape, if you do not include a save-set name with an input magnetic tape, BACKUP reads the next save set it encounters on the tape. (If you specify the input save-set qualifier /REWIND, BACKUP rewinds the tape and reads the first save set on the tape.)

Files-11 Disk Save Sets

To write save sets on a Files-11 disk, you must include the output save-set qualifier /SAVE_SET. The /SAVE_SET qualifier indicates to BACKUP that you want to create a save set, rather than a copy of the selected files, on the output volume. The disk must be mounted as a Files-11 volume; all volumes in a volume set must be mounted.

BACKUP can read a Files-11 save set as a Files-11 save set or as a sequential-disk save set:

When BACKUP reads a save set as a Files-11 save set, all volumes of the save set must be mounted. To read a save set that is not located in your process default directory, you must specify the directory in which the save set is located.

When BACKUP reads a Files-11 save set as a sequential-disk save set, you can mount the volumes one at a time. You must specify the master file directory [000000] in the save-set specification when reading a Files-11 save set as a sequential-disk save set.

A save set stored on a Files-11 disk is a standard file, however, and can be copied, renamed, deleted, or backed up.

Network Save Sets

You can create or read a network save set on a Files-11 disk attached to a remote node by specifying the node name of a remote node in the save-set specification. A remote node is accessible to the node you are working on (the host node) over a network. The network save set must be located on a publicly accessible disk (a disk mounted from the remote node with the /SYSTEM, /GROUP, or /CLUSTER qualifier) on the remote node.

Depending on the volume and file protection at the remote node, you may need to specify an access control string in the network save-set specification. An access control string includes the user name and password, and has the following format:remote_nodename"username password"::device_name:[directory]

Example

The following example creates a network save set on the remote node DOUBLE:

$ BACKUP

_FROM:[MY_DIR]
_TO:DOUBLE"username password"::DBA0:SAVEIT.BCK/SAVE_SET

Omit the access control string if it is not required to gain access to the remote node, such as in the case of proxy network access. Refer to the DECnet for OpenVMS Networking Manual for more information about access control strings and proxy network access.

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.

BACKUP can read a sequential-disk save set either as a sequential-disk save set or as a Files-11 save set:

When BACKUP reads a save set as a sequential-disk save set, the save set can be mounted one volume at a time. The default directory for the save set file specification is the master file directory [000000] on the disk.

When BACKUP reads a save set as a Files-11 save set, all volumes of the save set must be mounted. The default directory is your process default directory. Therefore, you must specify the master file directory [000000] in order to read a sequential-disk save set as a Files-11 save set.

Understanding the Backup Interfaces

Understanding BACKUP File Formats