Overwriting Media

By overwriting backups on media, the existing contents of the backup set are overwritten with the new backup, and therefore 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.

By default, Microsoft® SQL Server™ performs some checks to prevent backup media from being overwritten accidentally (even when you have specified that the media should be initialized). Backup media is not overwritten if either of the following conditions is met:

• The expiration dates for 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 given to identify the media easily.

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.

Note If the backup media is password protected, SQL Server does not write to the media. To overwrite media that is password protected, you need to reinitialize the media.

To overwrite media when creating a backup

See Also

sp_configure