Backup is the process of making a copy of information to be used in the event that the original copy is lost or damaged. The copy is typically transferred to a backup medium; i.e., either a virtual tape file, which is an allocation of disk space acting as a tape device, or any physical backup device supported by Windows, including the following:
Recordable CD-ROM (CDR)
Removable disk media
Tape (including Digital Linear Tape (DLT))
Virtual tape devices (virtual tape links or virtual tape files)
In subsequent text, the term backup medium or media will be used to include all of these backup and restoration devices.
Making backups of files on backup media is an important part of protecting data and ensuring the integrity of files. If a file is subsequently deleted by accident or if its data becomes corrupted, you can restore the most recent version of the file from backup media.
Generally speaking, the system administrator at each site should establish routine backup procedures for the entire system. However, application programmers should know enough about these procedures to understand what is being backed up and with what frequency.
For a complete discussion of the backup and restoration strategies and procedures, see Backing Up Files and Restoring Files and Accounts.
System Backup Commands
The following commands provide for the backup function, which copies either the file system or a single account from disk to backup media.
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ACCOUNT-SAVE |
A Proc that saves one account to the backup media. |
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FILE-SAVE |
A Proc that saves the entire data area of the disk to the backup media. |
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INCR-SAVE |
A Proc that saves to the backup media all changes made to the data area of the disk since the last full data backup. |
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LIST-FILE-STATS |
A Proc that lists statistics on all files most recently saved to backup medium. |
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SAVE |
Copies to backup media all or part of the data area of the disk. SAVE is invoked by all Procs used to make backup media. |
System Restoration Commands
These commands restore files by restoring information from backup media to disk.
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ACCOUNT-RESTORE |
Restores an entire account from ACCOUNT-SAVE backup media. |
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ADD-ACCOUNTS |
A Proc that restores all accounts that are present on a FILE-SAVE or ACCOUNT-SAVE backup medium, but are not on disk. |
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:FILELOAD |
Restores the entire data area of the database using any full file-save media (i.e., those made with the FILE-SAVE Proc). |
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RESTORE |
Restores dictionaries, data files, and accounts. |
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SEL-RESTORE |
Restores from backup media one or more items in a file; can be used only with a FILE-SAVE or an ACCOUNT-SAVE backup medium. |
These commands are available in the SYSPROG account and are documented fully in Using the SYSPROG Account and Commands.
The mvBase system also supports update and transaction logging. Transaction logging is a method of continuously backing up the system. It records changes made to a file at the moment the changes are made, and then writes the changes to backup media. Update and transaction logging provide an automatic audit trail; accidental data loss can be traced to a specific situation and reversed by simply restoring the data to a known state prior to the accident.
The process of logging item and file updates is called update logging. Processing update transactions and writing them to backup media is the actual transaction logging. Update and transaction logging can be done on a system-wide basis or it can be specified for selected files.
If your system employs update and transaction logging, see Update and Transaction Logging in the mvBase Operation and Administration Guide.
See Also