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1Clear out junk files and repair common Windows errors2Fix the driver behind crashes, sound loss and screen glitches3Repair Windows errors before they cause bigger problemsSuccessful data migration is more than copying files into new software. The strongest documented cases pair clean, governed data with staged changes, clear ownership, continuity planning, user and supplier involvement, and checks before and after cutover. Welsh Government, NHS England’s account of Dedalus, and Hackney Council show different ways to manage those tasks—and why a successful migration does not always mean switching everything at once.
What the success stories have in common
These examples concern public-sector services, mostly moving to cloud environments or internet delivery. They are not universal templates: the right sequence depends on security requirements, legacy dependencies, data condition, and the amount of disruption users can tolerate.
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Across the cases, the recurring lesson is organizational as much as technical. Teams prepared data and services before cutover, coordinated the people responsible for the old and new environments, and treated validation and continuity as part of the migration rather than afterthoughts. The reported outcomes belong to their individual projects; they are not benchmarks or promises for other organizations.
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Repair Windows errors before they cause bigger problemsFix Now →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Welsh Government: prepare the data before the transfer window
Welsh Government’s Future ICT project moved systems and services to the cloud between 2016 and 2019. Planning for public cloud began in 2014, but the project delayed the move when available functionality and security did not meet its needs. Later, it prioritized services using security assurance and cyber-vulnerability analysis, beginning with changes less visible to users. Legacy systems remained in place while the new architecture took over gradually.
Records policy made a large transfer manageable
The records move was the project’s hardest part: at least 33 million documents, about 20 terabytes, for an Electronic Records and Document Management System that had to remain constantly available. Old and new systems needed to stay in sync. The team used a secure VPN transit and supplier utilities to bulk-copy files and synchronize changes.
The Welsh Government case study, published in 2020, says the transfer took two weeks after two years of introducing and enforcing a strict records-management policy. The case attributes cleaner, easier-to-migrate data to that preparation. The useful point is not that every organization can move this volume in two weeks; it is that data cleanup and governance can shift effort out of the cutover period.
Keep a hybrid transition when dependencies require it
Some services and data remained on premise because of security needs or the age of their systems. A hyper-converged environment supported services that could not yet transition and held backup copies of important cloud datasets. This was a staged migration, not a failure to finish: the project moved what was ready while maintaining the dependencies that still mattered.
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The project also combined business and change management, digital, communications, and engineering work using an Agile approach. Ongoing outsourced operations remained distinct from the in-house project team, helping preserve business-as-usual support while transformation work proceeded.
NHS England and Dedalus: rehearse, validate, then improve the method
Dedalus decided in 2020 to move its UK data-centre services to a healthcare cloud environment. NHS England’s case study describes an 18-month programme covering 56 migrations, completed before the March 2022 deadline. The work included making solutions cloud-compatible and developing a safe method to extract existing data and load it into the enhanced solution.
Make readiness work explicit
Preparation involved technical suppliers from the beginning, initiation documents, customer-specific project plans, and cutover plans. Technical workshops helped align requirements and expectations. NHS trusts had bounded but important readiness responsibilities:
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- Check record counts before and after migration.
- Validate integrations.
- Carry out user acceptance testing in relevant areas.
- Take part in a dress rehearsal.
- Complete cutover activities.
This division of work matters: a supplier can move data, but the customer is often best placed to confirm that records, integrations, and workflows behave as expected in its own setting.
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Use the first wave to refine later waves
After the first migration, Dedalus conducted a lessons-learned exercise and changed its approach to AWS Data Migration Service. NHS England’s case says this reduced downtime and that the learning was incorporated into subsequent deployments. The case reports that 11 solutions were migrated in 10 days.
Dedalus described the programme as “a complete success” and said it completed the 56 migrations ahead of the deadline. NHS England’s case also reports an average 40% performance improvement for trust end users, and 220 platform or infrastructure incidents in the six months before migration compared with 55 in the six months after. These are project-specific figures reported in the case study, not independently established estimates of what another migration should achieve.
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Hackney Council: success can mean moving selected services
Hackney wanted to move services away from the Public Services Network toward internet delivery, with goals including improved user experience, data sharing, and continuous security monitoring. It moved email to Google’s G Suite but retained the PSN for services such as Blue Badge and DWP access. Its example shows why the boundary of a migration should be deliberate: some services can move while others still depend on the legacy network.
According to the Government Digital Service account, Hackney used planning workshops to agree principles, consider proposed solutions, explain benefits, and gain buy-in rather than impose a predetermined plan. An impartial technology leader’s senior support was also useful. The email move took about four months after approval of the business case and budget. Deciding whether archive mailboxes and distribution lists were still needed accounted for much of the complexity—a reminder that migration planning includes deciding what should not be carried forward.
A contrasting example: a concentrated payroll cutover
Deloitte’s vendor-authored case describes a state agency moving SAP payroll and reporting to AWS. The team created a detailed playbook spanning data, applications, networks, testing, quality assurance, production, and security, coordinating agency and state IT teams. Deloitte says the initial cutover used customized SAP export and import methods in a 12-hour window.
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Deloitte reports a 50–60% reduction in monthly payroll and batch runtime, an estimated annual saving of 70 working days for HR processing, 99.95% system availability on AWS, and 16 weeks from planning to initial migration. It also associates more than 10,000 users with the migrated data. Deloitte’s page did not establish a publication year, and these vendor-reported results should be treated as that project’s account, not an independent benchmark.
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The cases illustrate staged transitions, hybrid arrangements, and a concentrated cutover. They do not establish one universally best approach. Compare options against the conditions that determine whether users can keep working and whether the organization can verify the result:
- Continuity and downtime: Identify which services must remain available and how long any interruption is acceptable.
- Security and regulatory requirements: Establish assurance needs before choosing sequence or destination.
- Data quality and transformation: Assess cleanup, retention, formats, and how much reshaping the target system requires.
- Legacy dependencies: Map integrations, networks, and services that cannot move together.
- Capacity and performance: Define expected workloads and how performance will be checked after migration.
- Skills and supplier readiness: Confirm who owns extraction, loading, integration testing, and issue resolution.
- Validation and recovery: Agree record checks, rehearsals, cutover authority, and continuity or rollback arrangements.
- Total transition effort: Consider the work of running old and new environments in parallel as well as the migration itself.
A practical sequence for reducing migration risk
- Set ownership and rules. Assign data owners and agree retention, formats, cleanup standards, and what is out of scope. Welsh Government’s experience shows how enforcing records policy before transfer can improve readiness.
- Inventory services and dependencies. Classify each service by security needs, readiness, user impact, and connections to legacy systems. Decide which services can move first and which need to remain temporarily.
- Plan capacity and continuity. Make sure business-as-usual support continues while a dedicated team handles the transformation where capacity allows. Specify how old and new services will coexist and how data changes will be synchronized.
- Bring users and suppliers into planning. Use workshops to explain the reason for change, surface operational needs, and settle responsibilities. Involve technical suppliers early enough to align extraction, integrations, testing, and cutover.
- Write customer-specific cutover plans. Name the people responsible for record counts, integration checks, user acceptance testing, dress rehearsal, cutover decisions, and recovery or continuity actions.
- Rehearse and validate. Test the migration path and confirm that sample or migrated records, integrations, and relevant workflows meet agreed criteria. Define what evidence is required before declaring a wave complete.
- Review each wave against a baseline. Record downtime, incidents, performance, and completion against the measures chosen for the project. Investigate surprises and revise the method before the next wave; Dedalus’s reported change after its first migration is a concrete example.
How to interpret migration success figures
Case studies provide useful process details, but their metrics are tied to a particular project and publisher. NHS England’s Dedalus account and Deloitte’s vendor-authored payroll case report favorable outcomes; neither establishes that similar results are typical. Before using a figure to set expectations, ask what was measured, for which users or systems, over what period, and against which baseline. A credible success measure should be defined before cutover and reported with its scope, source, and comparison period.
The examples support a practical definition of success: the intended services and data are usable, checks pass, users can continue their work, and remaining dependencies are managed intentionally. That definition is more useful than treating a large transfer or a deadline alone as proof that an implementation went well.
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