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Introduction to Digital Preservation: Migration

Subjects: Digital Library

What is migration?

Also known as file format migration or sometimes called file format conversion, migration is different from storage media migration and software refresh. It involves transferring, or migrating, data from an aging or obsolete file format into a new file format, possibly using new applications systems at each stage to interpret the information. Moving from one version of a file format to a later version is a standard practice of migrations. This preservation action is particularly useful when the software used to render the file format type is now obsolete and modern software cannot render it correctly. This is the case with older word processing file formats, such as those created by obsolete software like WordPerfect or WordStar.

For more information, please visit the DPC Handbook on Preservation Actions.

Example of why we migrate files

Migration is important. Context is lost when modern software cannot render a file format type correctly. The example below shows what a Corel WordPerfect 7 file looks like in modern software.

      

Opened in LibreOffice Writer                                                      Opened in Microsoft Word 2007

Neither of these versions accurately represents what was intended by the original file, which can be seen rendered correctly in Corel WordPerfect version 7 below:

In migration, this file would be changed to another file format type, perhaps a Microsoft Word 2007 (.docx) file or an Adobe PDF document, depending on what is determined to maintain the most significant properties of the file and taking into account the policies of the organization. Migration is not done without significant research first.

Image source: Euan Cochrane, CC-BY 2.0

Benefits & drawbacks

When software used to render a file format is obsolete, one method of accessing the data is through file format migration. 

It also allows the data to be opened with modern, up-to-date software, thus making access easier for users.

However, it is important when undertaking file format migration to always retain the original file along with the new migrated file. There may very well be a loss to certain properties of the original file when file format migration is undergone.

It is important to assess what is considered an acceptable loss (if any). This will require understanding what is most important about the file and why it is part of the collection.

It is also important to consider how often to migrate a file format as it may not be practicable to migrate with every new file format version, but instead wait until there is a new generation file format type entirely.

But waiting too long may mean the software becomes obsolete before migration and therefore makes the task of migration harder to preform.