long time backup
Long-term archiving, also known as cold storage, is characterized by an unspecified period of time, which may well be years, decades or centuries. In this time frame, not only the file formats change, but also the application programs, operating systems and storage media.
The content ofdigital documents can be reduced to the information between"zero" and "one". However, in order to be able to interpret the zeros and ones, special interpreters are required, which can be recognized by the file extensions. Since each application program generates its own file formats, file formats can be read reliably only if the interpreter is present, with which the data were created. This fact already forms a large problem field for the long-term storage, since data formats are frequently changed with new software versions.
Requirements for long-term archiving
In the case of long-term archiving, if one wants to avoid backward compatibility via import filters, the programs and their various versions with which the data were created would also have to be stored in addition to the data. Or one uses for the archiving data formats, which are not subject to any change. For example, ASCII for texts, JPEG for images and the Portable Document Format( PDF) for documents. With PDF/A, the International Standards Organization( ISO) has standardized a file format for long-term archiving.
Other requirements for long-term archiving include the integrity of the document, it must be possible to display the stored data using simple tools, and the quality of the data must remain unchanged. In addition to the data and program issues, the operating system on which the application runs must also be archived. Another problem area is storage media, whose technologies, storage methods and playback devices are subject to constant change. In this case, the storage of old devices cannot necessarily help, since the interfaces, device drivers and controllers would also have to be archived.
For long-term archiving, there is the international reference model Open Archival InformationSystem( OAIS) defined under ISO 14721.