An important aspect of digital continuity is digital preservation. Many records have retention periods longer than the life of the systems they are captured in. Digital preservation requires a proactive program to identify records at risk and take necessary action to ensure their ongoing viability.
Preserving digital and audiovisual information and records may require migration to new platforms and formats. Regular and planned migration helps avoid obsolescence and ensures information continues to be accessible and usable.
Digital records are subject to three potential forms of obsolescence:
- File format obsolescence: vendors and creators of file formats can update their file formats with new versions, introducing compatibility issues; or they may withdraw support for a file format completely.
- Software obsolescence: the application or software which is needed to render file formats may change; and there may be withdrawal of support for software. This risk also applies to entire operating systems.
- Hardware obsolescence: computer hardware and storage are also subject to obsolescence. Computer technologies change very quickly and storage media and devices can become obsolete within a few years. Digital records stored on obsolete hardware can be difficult and expensive to recover.
Preservation techniques which can minimise the risk of digital records becoming inaccessible include:
- Bit preservation, which is a minimum level of digital preservation characterised by the following features:
- Fixity checking, validation, monitoring and reporting
- Multiple independent and geo-redundant copies
- Different flavours of storage technology
- Media replacement built into the procurement cycle
- Documented audit trails
- Robust disaster planning and access controls.
- Migration of digital records from an at-risk or obsolete format to a newer format which can be supported, noting that some formats cannot easily be migrated such as some CAD and CAM files.
Emulation is a less common preservation strategy that involves accessing the obsolete digital record using the software originally used to create and render it. Where the cost of migrating a particular format is high, for example for some CAD and CAM formats, emulation may be a viable and cost-effective preservation strategy.
Factors influencing which preservation strategy is best for your agency will include:
- an assessment of your records that require long term preservation
- the technology you currently have, and are likely to acquire in the near future
- the most financially feasible option, based on a risk analysis and taking into account your agency's accountability obligations
- the long term implications for the integrity of your records of any preservation processes adopted.
See Preserving information for a full list of preservation planning resources. Preservation is just one aspect of managing digital information to ensure that it can be used in the way that is required for as long as required, and no longer. For more information on managing digital records, see Types of information and systems or contact the Agency Service Centre.