Designing the migration strategy and approach is a key component and driver for future planning. Produce a draft migration schedule and timetable of migration events. The migration approach takes input from the migration plan and all discovery activities. It analyses these inputs to create a set of repeatable migration activities that describe the techniques and tools used for each technology and a migration approach which describes the lower level detail for each migration phase.
Data is stored on various media in files or databases, and is generated and consumed by software applications which in turn support business processes. The need to transfer and convert data can be driven by multiple business requirements and the approach taken to the migration depends on those requirements.
A business may choose to rationalize the physical media to take advantage of more efficient storage technologies. This will result in having to move physical blocks of data from one tape or disk to another, often using virtualization techniques. The data format and content itself will not usually be changed in the process and can normally be achieved with minimal or no impact to the layers above.
Similarly, it may be necessary to move from one database vendor to another, or to upgrade the version of database software being used. The latter case is less likely to require a physical data migration, but this can happen with major upgrades. In these cases, a physical transformation process may be required since the underlying data format can change significantly. This may or may not affect behavior in the applications layer, depending largely on whether the data manipulation language or protocol has changed – but modern applications are written to be agnostic to the database technology so that a change from Sybase, MySQL, DB2 or SQL Server to Oracle should only require a testing cycle to be confident that both functional and non-functional performance has not been adversely affected.
Changing application vendor – for instance a new CRM or ERP platform – will inevitably involve substantial transformation as almost every application or suite operates on its own specific data model and also interacts with other applications and systems within the enterprise application integration environment. Furthermore, to allow the application to be sold to the widest possible market, commercial off-the-shelf packages are generally configured for each customer using metadata. Application programming interfaces (APIs) may be supplied by vendors to protect the integrity of the data they have to handle.
Migration as a form of digital preservation
Migration, which focuses on the digital object itself, is the act of transferring, or rewriting data from an out-of-date medium to a current medium and has for many years been considered the only viable approach to long-term preservation of digital objects. Reproducing brittle newspapers onto microfilm is an example of such migration.
Migration addresses the possible obsolescence of the data carrier, but does not address the fact that certain technologies which run the data may be abandoned altogether, leaving migration useless.
- Time-consuming: migration is a continual process, which must be repeated every time a medium reaches obsolescence, for all data objects stored on a certain media.
- Costly: an institution must purchase additional data storage media at each migration.
- Define the implementation and migration plan.
- Evaluate the options (pros & cons) for each key decision.
- Define high level implementation and migration approach.
- Review and confirm the migration runbook.
- Run key decisions workshop to review and confirm the migration approach.
- Secure approval for key decisions.
- Review and update migration plan following key decisions workshop.
- Analyse all workload characteristics.
- Analyse the route to live environments and tooling.
- Define migration activities for all platforms and applications.
- Define the overall migration approach describing the migration phases.
Hints and tips
- This is a critical activity that forms the heart of the job. Take care to make quick decisions but put in the staff work and consultation to make good decisions.
- Use analysis and logical processes to make decisions and follow fact-based methods.
- Understand and document the batch environment and treat as a required solution element, especially where batch is distributed hierarchically and centrally scheduled.