Document revision date: 15 July 2002

When formulating a backup strategy, keep in mind the specific requirements of your site and the advantages and disadvantages of the different types of backups. Your backup strategy also depends on the following factors:

• The resources you can devote to backups
• The importance of the data
• The volatility of the data

For example, if you have a standalone workstation, a nightly image backup might be your best approach.

Under other circumstances, you might want to choose some combination of image and incremental backups. For example, daily image backups might be inconvenient if your system always has interactive users logged in. You could choose to perform a weekly image backup and nightly incremental backups.

Table 11-1 compares image and incremental backups.

Table 11-1 Comparison of Image and Incremental Backups

Backup Type	Advantages	Disadvantages
Image	Faster to restore than incremental backups. Backs up entire disk.	Uses more space and time than incremental backups. Requires that no interactive users are logged in because of the effect on system performance and because of open file considerations (see Section 11.15.1).
Incremental	Takes less time and media storage space.	More difficult to restore files. Still requires periodic image backups.

You do not have to change tapes or disks during a backup if any of the following statements is true:

• All of the files fit on a single piece of storage media.
• Your site uses a tape loader.
• You have several disk or tape drives available.

In these cases, the backup can be performed by a batch job that runs late at night or at some other time when interactive use of the system is likely to be at a minimum. Section 11.15.7 contains some sample command procedures that you can run in a batch job to back up your disks.

11.4 Understanding the Backup Interfaces

Two interfaces are available to the OpenVMS Backup utility:

• The BACKUP command, which is a command in the DCL command line interface
• The Backup Manager, which is an interactive screen-oriented interface

To back up files, you must specify what you want to back up (the input) and where you want BACKUP to place the resultant save set or file (the output). You can also use BACKUP qualifiers to perform different functions depending upon their position on the command line:

BACKUP/qualifiers input-specifier/qualifiers output-specifier/qualifiers

Table 11-2 lists the types of BACKUP command qualifiers.

Table 11-2 BACKUP Command Qualifier Types

Type	Position	Effect
Command qualifier	Anywhere on the command line	Affects both input and output specifiers.
Input specifier qualifier	Directly after the input specifier	Affects only the input specifier.
Output specifier qualifier	Directly after the output specifier	Affects only the output specifiers.

When you use BACKUP, make sure you place BACKUP qualifiers in their correct positions on the command line. For more information about the BACKUP command line, refer to the OpenVMS System Management Utilities Reference Manual.

11.4.1.1 Using Extended Character Sets

Beginning with OpenVMS Version 7.2, which introduces Extended File Specifications, BACKUP can process file names that have extended character sets. Included are the following formats:

• ODS-2 standard file name
• ISO Latin-1
• Unicode (UCS-2)

For additional information about extended character sets, refer to the OpenVMS User's Manual.

11.4.1.2 Specifying Input Files

For file-based BACKUP operations, you can specify relative input file versions, for example:

$ BACKUP FILE.DAT;-2 SAVED_FILE.DAT

This example shows that you can choose the second-from-the-most-recent version of the input file and assign it a different file name.

With BACKUP, you cannot use -0 as a relative file version to specify the earliest version of the file. BACKUP processes -0 as if it were 0, saving the most recent version of the file for processing.

11.4.2 The Backup Manager

Backup Manager is a screen-oriented interface to the OpenVMS Backup utility (BACKUP) that presents BACKUP's capabilities in an intuitive, task-oriented, self-documenting manner. Backup Manager can ease backup tasks by guiding you through the backup process. No real performance differences exist between using the Backup Manager and using the BACKUP command line.

Backup Manager runs on:

• Any Compaq VTxxx-series video display terminal or equivalent terminal emulator
• VMS VAX Version 5.4 or higher systems, and OpenVMS Alpha Version 1.5 or higher systems

The Backup Manager interface is based on the OpenVMS Screen Management Run-Time Library (RTL) routines.

11.4.2.1 Backup Manager Features

Backup Manager can perform the following backup operations:

• Save an entire volume to a save set
• Save selected files from a volume to a save set
• Restore an entire volume from a save set
• Restore selected files from a save set
• List a save set

Three types of online assistance are available with Backup Manager:

• Context-sensitive help
  Press PF2 or the Help key to get help about the object at which the display cursor is currently located.
• Context-sensitive hints
  You are prompted for input by a one-line "hint" about the field where the display cursor is currently located.
• Pull-down help
  Choose the pull-down Help menu bar item for more extensive help on a variety of Backup Manager topics.

To start Backup Manager, enter the following command at the DCL prompt:

$ RUN SYS$SYSTEM:BACKUP$MANAGER

Output from the Backup utility is automatically displayed when an operation starts. You can suspend output at any time (Ctrl/P) and scroll through it. You can also use Ctrl/T to display status or Ctrl/C to stop the current BACKUP operation.

11.5 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. Table 11-3 lists the types of media that you write a save set to.

Table 11-3 Save-Set Types

Media Type	For More Information
Magnetic tape	Section 11.5.1
Files--11 disk	Section 11.5.2
Files--11 disk on a remote node (network save set)	Section 11.5.3
Sequential disk	Section 11.5.4

11.5.1 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.

Compaq 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:

WKLY27JAN2000.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.)

11.5.2 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.

11.5.3 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.

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.

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.

On VAX systems, BACKUP saves files and directories from Files--11 Structure Level 1 and 2 disks to disks or magnetic tapes. If necessary, you can use BACKUP to restore the saved files and directories to Files--11 Structure Level 1 and 2 disks.

If a VAX system performs image backup of an Alpha system disk, a restore operation causes the Alpha system to reboot successfully.

On Alpha systems, BACKUP can save files and directories from Files--11 Structure Level 2 or 5 disks to either disks or magnetic tapes. If necessary, you can use BACKUP to restore the saved files and directories to Files--11 Structure Level 2 or 5 disks.

You cannot back up files on ISO 9660-formatted media, but you can restore save sets stored on ISO 9660-formatted media.

For more information about the Files--11 disk structure, see Section 9.1.1.2. For more information about ISO 9660 devices, see Section 8.2.2.

11.7 Setting Process Quotas for Efficient Backups

You can optimize the efficiency of backups on your system by properly setting the process quotas for the process from which backups will be made (the process from which you enter the BACKUP command or submit your backup command procedure). This is especially important if you are using a streaming tape drive.

How to Perform This Task

To set process quotas for efficient backups, perform the following actions:

1. Determine which account you want to use for backups. You can use an existing account, or create one solely for backups. For information about creating accounts, see Section 7.6.
2. Use the Authorize utility (AUTHORIZE) to determine the current quota values for the account you will use for backups. For example, if you are using the SYSTEM account for backups, enter the following commands:

   $ SET DEFAULT SYS$SYSTEM $ RUN AUTHORIZE UAF> SHOW SYSTEM

3. Using the System Management utility (SYSMAN), determine the value of the system parameters WSMAX and CHANNELCNT, as follows:

   $ RUN SYS$SYSTEM:SYSMAN SYSMAN> PARAMETERS SHOW WSMAX %SYSMAN-I-USEACTNOD, a USE ACTIVE has been defaulted on node DIEM Node DIEM: Parameters in use: ACTIVE Parameter Name Current Default Minimum Maximum Unit Dynamic -------------- ------- ------- ------- ------- ---- ------- WSMAX 2600 1024 60 100000 Pages SYSMAN> PARAMETERS SHOW CHANNELCNT Parameter Name Current Default Minimum Maximum Unit Dynamic -------------- ------- ------- ------- ------- ---- ------- CHANNELCNT 127 127 21 2047 Channels SYSMAN> EXIT $

   
   In this case, the values for WSMAX and CHANNELCNT, as shown in the column marked Current, are 2600 and 127, respectively. Use these values to help set the correct values for the process quotas.

4. Use AUTHORIZE to compare the values for the process quotas to the recommended values for efficient backups, as shown in Table 11-4.

   Table 11-4 Recommended Process Quotas for Efficient Backups

   Process Quota	Recommended Setting
   WSQUOTA	Equal to system parameter WSMAX
   WSEXTENT	Equal to WSQUOTA quota
   PGFLQUOTA	Equal to or greater than WSEXTENT quota
   FILLM	Less than system parameter CHANNELCNT
   DIOLM	Either 4096 or three times the value of FILLM quota, whichever is greater
   ASTLM	Either 4096, at least 100 greater than DIOLM quota, or three times the value of FILLM quota, whichever is greater
   BIOLM	Equal to FILLM
   BYTLM	Equal to or greater than the following value: (256*FILLM)+(6*DIOLM)
   ENQLM	Greater than FILLM quota

5. If necessary, change process quotas using the AUTHORIZE command MODIFY. If you change process quotas, you must log out and log in again for the changes to take effect. For information about changing these process quotas, see Section 7.7.2.
   Table 11-5 lists a set of process quota values that are appropriate for many configurations. If your disks are highly fragmented or if your backups will be performed during periods of heavy system use, you should reduce the values shown for WSQUOTA and FILLM.

   Table 11-5 Sample Process Quotas for Efficient Backups

   Process Quota	Suggested Value
   WSQUOTA	16384
   WSEXTENT	Greater than or equal to WSQUOTA
   PGFLQUOTA	32768
   FILLM	128
   DIOLM	4096
   ASTLM	4096
   BIOLM	128
   BYTLM	65536
   ENQLM	256

Example

The following steps show the commands that you would use to run the Authorize utility and set process quotas for the SYSTEM account (if you plan to run backups from a different account, determine the process quotas for that account):

1. Determine the current quota values:

   $ SET DEFAULT SYS$SYSTEM $ RUN AUTHORIZE UAF> SHOW SYSTEM Username: SYSTEM Owner: SYSTEM MANAGER Account: SYSTEM UIC: [1,4] ([SYSTEM]) CLI: DCL Tables: DCLTABLES Default: SYS$SYSROOT:[SYSMGR] . . . Maxjobs: 0 Fillm: 40 Bytlm: 32768 Maxacctjobs: 0 Shrfillm: 0 Pbytlm: 0 Maxdetach: 0 BIOlm: 18 JTquota: 1024 Prclm: 10 DIOlm: 18 WSdef: 256 Prio: 4 ASTlm: 24 WSquo: 512 Queprio: 0 TQElm: 20 WSextent: 2048 CPU: (none) Enqlm: 200 Pgflquo: 20480 . . . UAF> EXIT %UAF-I-NOMODS, no modifications made to system authorization file %UAF-I-NAFNOMODS, no modifications made to network authorization file %UAF-I-RDBNOMODS, no modifications made to rights database $

   
   In this example, SYSTEM has the following quotas:

   WSQUOTA	512
   WSEXTENT	2048
   PGFLQUOTA	20480
   FILLM	40
   DIOLM	18
   ASTLM	24
   BIOLM	18
   BYTLM	32768
   ENQLM	200

2. Using the System Management utility (SYSMAN), determine the value of the system parameters WSMAX and CHANNELCNT, as follows:

   $ RUN SYS$SYSTEM:SYSMAN SYSMAN> PARAMETERS SHOW WSMAX %SYSMAN-I-USEACTNOD, a USE ACTIVE has been defaulted on node DIEM Node DIEM: Parameters in use: ACTIVE Parameter Name Current Default Minimum Maximum Unit Dynamic -------------- ------- ------- ------- ------- ---- ------- WSMAX 2600 1024 60 100000 Pages SYSMAN> PARAMETERS SHOW CHANNELCNT Parameter Name Current Default Minimum Maximum Unit Dynamic -------------- ------- ------- ------- ------- ---- ------- CHANNELCNT 127 127 21 2047 Channels SYSMAN> EXIT $

   
   In this case, the values for WSMAX and CHANNELCNT, as shown in the column marked Current, are 2600 and 127, respectively.

3. Compare the values for SYSTEM to the values in Table 11-4, and set the appropriate values:

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