UC-2.3

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UC-2.3 Media Replacement
Summary
Number	UC-2.3
Name	Media Replacement
Context	UC-2 Archival Storage
Sub-Use Cases	None
Overview	Replace Media refreshes and replicates physical storage media; Replace Media performs straightforward repackaging of AIP.
Actors	Replace Media
Description
Preconditions	UC-2.1 Receipt of AIP
Trigger	No direct trigger. Policy decision whether to migrate, refresh, or repackage, and when this occurs, and to which AIPs. Replace Media just provides the capability.
Successful outcome	Storage media are refreshed or replicated; AIPs are repackaged without altering Content Information and Preservation Description Information
Steps	Replace Media refreshes or replicates AIP according to migration strategy (OAIS Page 4-7) Replace Media performs straightforward repackaging of AIP (for example, migrating them to new media under a new operating system and file system) without altering Content Information and Preservation Description Information (OAIS Page 4-7)
Exceptions
Documentation
Citations	OAIS page 4-7, section 4.1.1.3 "The Replace Media function provides the capability to reproduce the AIPs over time. Within the Replace Media function the Content Information and Preservation Description Information (PDI) must not be altered. However, the data constituting the Packaging Information may be changed as long as it continues to perform the same function and there is a straight forward implementation that does not cause information loss. The migration strategy must select a storage medium, taking into consideration the expected and actual rates of errors encountered in various media types, their performance, and their costs of ownership. If media-dependent attributes (e.g., tape block sizes, CD-ROM volume information) have been included as part of the Content Information, a way must be found to preserve this information when migrating to higher capacity media with different storage architectures. Anticipating the terminology of section 0, this function may perform ‘Refreshment’, 'Replication’, and ‘Repackaging’ that is straightforward. An example of such ‘Repackaging’ is migration to new media under a new operating system and file system, where the Content Information and PDI are independent of the file systems. However, complex ‘Repackaging’ and all ‘Transformation’ are performed under Administration supervision by the Archival Information Update function to ensure information preservation. Refer to section 0 for a detailed description of migration issues."
Diagrams
Notes
	No other part of system acting directly on Replace Media.