Modernising Legacy Systems: When and How to Do It Correctly

Many organisations rely on legacy systems that were built decades ago using older technologies. While these systems served their purpose in the past, keeping them running comes with many drawbacks in today's digital era. Legacy system modernisation provides a solution, but it's a complex undertaking that requires careful planning and execution.

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What are Legacy Systems?

Legacy systems refer to old software applications and hardware infrastructure built on outdated languages, platforms and architectures. They often run core business functions and contain critical data assets. Examples include mainframe systems, monolithic apps built before client-server, green screen terminals, etc.

These systems have typically been patched, extended and customised repeatedly over the years. While they continue to run core processes, integrating new functionalities and demands becomes challenging. Lack of documentation and dependency on scarce skills further complicate maintenance. All these solutions require legacy modernisation services to maintain productivity and competitiveness.

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Key Drivers for Modernisation

There are some clear signals that suggest legacy systems are ripe for modernisation:

• Inability to meet new demands - New features, integration needs, volumes and performance needs cannot be supported.
• Rising maintenance costs - Keeping outdated systems running requires expensive manual effort. Vendor support may no longer exist.
• Security risks - Old systems weren't built for modern cyberthreats. Data is vulnerable.
• Dependency on scarce skills - Few people have expertise in outdated languages and platforms. Knowledge drain as veterans retire.
• Vendor or hardware obsolescence - Components are reaching end-of-life with no support or replacements available.
• Compliance and audit issues - Inability to adhere to regulatory mandates around data controls, reporting etc.

These pain points impose substantial technical debt and business risk. Modernisation provides solutions but should be well-planned. By continuing to use old-fashioned tech stacks, 90% of businesses are putting themselves at a disadvantage. In other words, even though your legacy technology was important in the past, it will never help you get to where you need to be or want to be in order to continue down a successful path in the future.

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Key Modernisation Strategies

When embarking on a legacy modernisation initiative, organisations must carefully assess their systems and choose the right strategies to modernise different applications and components. The strategy has to align with business objectives, timelines, budgets and application architecture. There are pros and cons to each approach that must be evaluated.

The most suitable strategy often depends on factors like how mission-critical the system is, acceptable downtime, application structure, complexity of integrations, availability of skills and more. Many organisations take an incremental, phased approach, applying different techniques to various systems and components.

Some common modernisation strategies include:

Replatforming (Lift and Shift)

This strategy involves migrating an application to a new infrastructure or platform without changing code. For example, moving from mainframe or legacy servers to cloud servers, replacing COBOL with C# by recompiling source code, etc. This is the fastest way to achieve modernisation but lacks flexibility beyond the initial migration.

Replatforming is suited for less complex, standalone legacy systems where future change is unlikely. The "Lift and shift" approach gets systems onto modern platforms quickly.

Rehosting

Similar to replatforming, it also upgrades the operating system, databases, runtime libraries and other software components. For instance, migrating from legacy Unix servers to Linux or Windows servers in the cloud. Or upgrading from legacy databases like IDMS to modern SQL Server.

Rehosting provides more future proofing while still minimising code changes. It is a relatively low-risk approach providing short-term agility benefits and more extensibility relative to replatforming.

Refactoring

This enhances the internal structure of source code without changing external functionality. The goal is to improve design, remove duplication, enhance readability and maintainability for easier future change.

Refactoring is often done incrementally when adding new features to legacy apps. This streamlines the codebase for agility. However, refactoring alone does not change platforms or architecture.

Re-architecting

More extensive changes to application architecture and code. This may involve moving from monoliths to microservices, rewriting modules in new languages, enhancing UIs, integrating APIs and more. Re-architecting maximises future extensibility but requires the most effort initially.

Appropriate for complex, business-critical legacy apps where extensive future change is expected. Brings long-term flexibility but requires skills and testing.

Retiring

Scrapping obsolete legacy systems and replacing them with new off-the-shelf software is an option as well. This allows consolidating capabilities into modern integrated solutions. Requires data migration from old systems.

Makes sense when there is limited value in extending outdated apps with small user bases or where packaged solutions meet needs.

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Key Steps for Successful Modernisation

Modernising business-critical legacy systems that power core operations requires meticulous planning and execution:

1. Business Goal Alignment

   Projects must deliver clear business value tied to organisation objectives. Whether it's improving agility, lowering TCO, or managing risk, goals should guide plans.

2. Thorough Assessment

   A comprehensive audit examines system components, data models, dependencies, risks and metrics. This informs the strategy and roadmap.

3. Phased Roadmap

   Break initiative into smaller chunks to deliver value incrementally while minimising risk. Prioritise based on business needs.

4. Rigorous Testing

   Establish robust test environments and procedures. Validate performance, security and functionality thoroughly before going live. Consider test automation.

5. Data Migration

   Data migration planning is crucial. Meticulously cleanse, transform and load data into new systems. Retain access to legacy data as needed.

6. Documentation and Training

   Update all docs reflecting changes. Provide extensive end-user and admin training. Prepare operational guides.

7. Change Management

   Get stakeholder buy-in across businesses, vendors and IT teams. Address needs proactively through communications, training and support.

8. Ongoing Support

   Support old and new systems in parallel during the transition. Monitor issues closely. Have contingency plans for reverting if necessary.

    

Choosing the Right Modernisation Partner

Legacy modernisation needs specialised expertise across legacy environments, new platforms and integration. Partnering with experienced service providers can supplement internal capabilities. Look for:

• Proven experience with similar projects and domain expertise
• End-to-end capabilities spanning legacy systems, modern platforms and integrations
• Flexible engagement models - onshore, offshore, dedicated teams or managed services
• Automation expertise - tools, accelerators and frameworks to expedite modernisation
• Advisory services - to assess the current state, formulate a roadmap and govern the execution

The right partner brings specialised skills, assets and experience that allow balancing cost, risk and speed for optimal outcomes.

Weighing the Business Case

The upfront costs for modernising legacy systems can seem daunting. But the ROI in terms of agility, TCO reduction, and risk mitigation is substantial:

1. Future-proofing - Modern platforms provide flexibility to adapt to new demands
2. Productivity gains - Fewer failures and outages improve system reliability
3. Cost savings - Reduced maintenance needs lowers TCO by 60% or more
4. Risk reduction - Improved security, resilience and ability to meet compliance needs
5. Innovation enablement - Paves the way for digital transformation initiatives

Analysing these key benefits makes a compelling case for legacy modernisation investments.

Conclusion

Legacy modernisation, done right, can transform previously restrictive systems into extensible digital platforms aligned with business objectives. But it requires careful analysis, planning and execution. Working with experienced partners and taking an incremental approach is key to minimising disruption while maximising returns.

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Article by Pankaj Shah: DCP Web Designers London