Using Media Sets and Families

This topic discusses several considerations for using media sets and media families.


For recommendations about how to manage backup media, see Planning for Disaster Recovery.

Sequence Numbers

The correct order is important for multiple media families within a media set or multiple backup media within a media family. Therefore, backup assigns sequence numbers in the following ways:

  • Sequential media families within a media set

    Within a media set, the media families are numbered sequentially according to their position in the media set. The media-family number is recorded in the family_sequence_number column of the backupmediafamily table.

  • Physical media within a media family

    A media sequence number indicates the order of the physical media within a media family. The sequence number is 1 for the initial backup media. This is tagged with 1; the second (the first continuation tape) is tagged with 2; and so on. When the backup set is restored, the media sequence numbers make sure that the operator restoring the backup mounts the correct media in the correct order.

To view the media sequence and family sequence numbers

Considerations for Using Multiple Devices

When you use multiple tape drives or disk files, the following considerations apply:

  • For backup:

    The complete media set that is created by a backup operation must be used by all subsequent backup operations. For example, if a media set was created by using two tape backup devices, all subsequent backup operations that involve the same media set must use two backup devices.

  • For restore:

    For any restore from disk backups and for any online restore, all the all media families must be concurrently mounted. For an offline restore from tape backups, you can process the media families from fewer backup devices. Each media family must be processed completely before starting to process another media family. Media families are always processed in parallel, unless they are being restored with a single device.