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HP OpenVMS Systemsask the wizard |
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The Question is: what purpose does a standalone backup serve? The Answer is : Why standalone BACKUP? The same reason as any other backup operation, it allows you to archive a version of your data and your programs that can later be (reliably) restored. OpenVMS supports shared access to files, and file data caching in host memory. Both can have implications around the validity of a disk backup, as applications (or the operating system itself) can have files open for write access and the contents may not be in an entirely consistent state. This means that the files that are the target of the BACKUP should be quiescent when the BACKUP is made, to ensure that the data is in a consistent state. With files accessed by applications, getting a consistent BACKUP can involve shutting down the applications, or using mechanisms implemented within the application to ensure the file contents are consistent. To ensure a reliable copy of the OpenVMS operating system itself, you should use a copy of OpenVMS or standalone BACKUP (standalone BACKUP is available on OpenVMS VAX only) in order to ensure that the target system disk is entirely quiescent. OpenVMS holds a number of files open, and by nature of the operating system provides no way to achieve consistent BACKUPs of these open files. Standalone BACKUP can be on the same system disk as the operating system, on magtape media, or on another disk. An additional copy of standalone BACKUP should be available on alternative media for use in the event of a problem with the system disk, otherwise the restoration of the system disk from BACKUP could be, uh, "interesting". Standalone BACKUP can also be used to archive application data, though most sites use on-line BACKUP for this. For further information, please see the OpenVMS System Management manuals.
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