The first question to ask about a migration project is do you really want to? Maybe this is a strange question but I don’t think due consideration is given to the benefits of keeping two (or maybe more) solutions with duplicate capabilities.
Migrations broadly come from four sources:
(1) Acquisition: in general the goal of the migration is to move onto systems of either the acquiring or acquired organisation to realise cost-savings
(2) Divesture: sometimes an organisation sells a part of its offering; in this case it is only interested in the migration to remove data and systems it no longer requires
(3) Internal rationalisation of systems with the same motive as (1) but different politics
(4) Moving one system to a new, replacement, system
I don’t address (2) here as there is not an option for keeping more than one system but before undergoing the pain, and expense, of a migration for (1), (3) or (4) consider the benefits of having two:
- I have written about the size of effective groups when it comes to communication. Unless the result of the migration will be a significant reduction in the developers, ops, users, managers, customers, etc. then it becomes harder for the resulting ecosystem to be agile. Keeping two systems, and their surrounding ecosystems could give an organisation two agile components as opposed to a single rather more stodgy one.
- It’s easy to sell one part of the organisation if it is neatly packaged-up around its own system(s)
- The focus of each system can be different, and make use of different skills. For example one system could focus on retaining existing business whilst another can be focussed on acquiring new business.
- Some friendly rivalry between teams can help drive innovation
- Being aware there is another team that could take over the work of a team might help control pay demands but be careful teams don’t become over protective and put-up barriers (e.g. by hiding knowledge)
Also consider that a migration can be a major distraction and there may be other opportunities lost; if the business case is marginal then look for other opportunities before committing resources to a migration.