Overwriting Backup Media
By overwriting backups on media, the existing contents of the backup set are overwritten with the new backup and are no longer available. For disk backup media, only the files used by the backup device(s) specified in the backup operation are overwritten; other files on the disk are unaffected. When overwriting backups, the existing media header can be preserved, and the new backup is created as the first backup on the backup device. If there is no existing media header, a valid media header with an associated media name and media description is written automatically. If the existing media header is invalid, the backup operation terminates.
Backup media is not overwritten if either of the following conditions is met:
- The existing backups on the media have not expired.
The expiration date specifies the date the backup expires and can be overwritten by another backup. You can specify the expiration date when a backup is created. By default, the expiration date is determined by the media retention option set with sp_configure.
- The media name, if provided, does not match the name on the backup media.
The media name is a descriptive name used for easy identification of the media.
However, these checks can be explicitly skipped if you are sure you want to overwrite the existing media (for example, if you know that the backups on the tape are no longer needed).
If the backup media is password protected by Microsoft® Windows NT® 4.0 or Windows® 2000, Microsoft SQL Server™ does not write to the media. To overwrite media that is password protected, you need to reinitialize the media.
To create a database backup