Technology · Technical debt and renewal · Component
Renewal roadmap
The phased plan for replacing or modernising systems, sequenced so that the business keeps running throughout.
The deliverable
What it is
Large replacements carried out in a single step have a poor record. The pattern Fowler named the strangler fig offers an alternative: build the new system around the old, move one function at a time, and retire the old system once nothing depends on it.
The roadmap sets the sequence and the architecture of each step. Delivery itself runs as projects, planned in Time Core under project management, and the treatment of the data being migrated follows the retention rules held in Data Core.
One level in
What it is made of
Each element is a constituent part of the component. Follow one to see the attributes it carries.
Renewal step
One increment of replacement: the function being moved, from which system to which, and in what window.
4 attributes: Function moved · From system · To system · Planned window
LearnParallel running
How long old and new run side by side, how their results are reconciled, and what signals readiness to switch.
3 attributes: Parallel period · Reconciliation method · Switch criterion
LearnDecommissioning
The conditions and date for switching the old system off, including the archive of what must be kept.
3 attributes: Switch-off date · Archive location · Decommissioned
Learn
Set the switch-off date when the roadmap is written. Old systems left running after replacement are how estates double in size.
The other components in technical debt and renewal
Technical debt register
The known shortcuts and outdated parts of the estate, what each costs to carry, and what it would cost to repay.
LearnApplication portfolio assessment
Each system rated for business fit and technical condition, with the resulting course: tolerate, invest, migrate or eliminate.
Learn