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Legacy system migration best practices can ensure your migration strategy stays on track. Our guide will help you to successfully modernize your systems.


Legacy System Migration: Best Practices

Posted by Angela Davis on December 14, 2023
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Legacy system migration best practices are the strategies and steps that can help ensure a smooth migration process for your business. 

Legacy system migration can seem intimidating and expensive, but more organizations are realizing how vital it is for remaining competitive. Despite increasing digital transformation, much of the world still runs on aging mainframe computers. As recently as 2020, 95% of ATMs and many other financial systems still used COBOL—a programming language from the 1950s. Taking a legacy banking system offline for migration would cause severe disruption, so it’s no wonder that decision-makers don’t want to make changes that can affect productivity for days or even weeks.

But, the risks of legacy systems cannot be ignored. Troubleshooting becomes more costly, customer experiences decline, and cybersecurity falls behind industry standards. Read on to understand why legacy system migration is worth the time and effort, as well as the best practices that guarantee success.

Legacy banking systems are reliant on aging programming languages

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How can legacy application modernization and system migration actually save you money?

The initial outlay necessary to complete legacy system migration can make it unattractive to decision-makers. However, as the benefits of digital modernization include less troubleshooting and better security, it is actually cost-effective and leads to more profit in the long run. 

Let’s look at these factors in more detail to understand how they can contribute to reduced overheads after legacy application modernization. 


Troubleshooting a legacy system requires the right tools and expertise. For example, you may need subscriptions to middleware software to keep an older system compatible with new computers. 

Unfortunately, the experts needed to maintain these systems are becoming more rare, for example, many COBOL programmers are now retiring out of the workforce entirely. This further increases the costs of maintaining a legacy system. 

Time cost

Outdated legacy systems can also strain IT departments and be a drain on their productivity and resources. Rather than focusing on new, value-generating innovation, your specialist employees have to spend their time and energy keeping an out-of-date system running as well as possible.


As cybersecurity is constantly advancing, it’s easier for cybercriminals to attack legacy systems. The platforms underpinning credit card transactions were often built for a world before the Internet, while email was created for an Internet before the World Wide Web, leaving them less protected.

There are two kinds of cyber attackers: those who know the system inside out, and those who are just re-trying recent exploits on systems that haven't been updated. Over time, legacy systems become vulnerable to both, and cyberattacks can prove incredibly costly for an organization.

Global cybercrime is estimated to cost $190,000 every second

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Best practices for creating a successful cloud migration strategy for your organization

Understanding how important the migration of legacy systems is and knowing how to enact it are very different things. Using these legacy system migration best practices will ensure you can swiftly and securely update your systems and benefit from up-to-date technologies.

Study your current system

Everything in your legacy system happens for a reason. However, legacy code is often written by developers who no longer work for a company, meaning that in the worst-case scenario, no one at your company actually understands how the system works.

If you start your cloud migration strategy without studying your current system, you might miss a feature or process that turns out to be business-critical, resulting in disastrous consequences for your company.

To ensure a successful migration, start by conducting a thorough analysis of your current tech stack. How does it work and why does it work in that way? What security provisions does it have? Employees might have grown to resent the old system, but there could be good business decisions built into it that are worth preserving for the future.

Understand your business goals

Why are you migrating to a new system at all? Understanding the business goals your system has to serve is essential for a successful migration as it enables you to design a more efficient cloud infrastructure, which will meet your current needs and support future growth at its center.

Begin by identifying the KPIs your system impacts and think about how you can design your new system to serve these. This keeps your migration closely aligned with the long-term goals of your business. You can also use KPIs to evaluate the success of your migration once it’s complete. 

Know the importance of modernization

It's crucial that everyone in the company understands the importance of legacy application modernization.

Once you've established how it aligns with your business goals, you can use this information to achieve buy-in from the wider company. This is a big project, so it's important to communicate to stakeholders how the new system will make their lives easier and their teams more efficient.

Break your migration down into phases

Migration is a major project, so it’s useful to break it down into smaller parts. This makes it easier for all teams to understand what’s happening and allows you to keep track of your accomplishments. Some essential phases for a cloud migration strategy  are:

Choosing a cloud provider

Once you have a clear understanding of your requirements and goals, select a cloud service provider that can fulfill these. Make sure to consider cost, performance, features, security, compliance, and vendor reputation.

Design and configuration

Design and configure your cloud environment based on your migration plan. This stage should involve setting up virtual machines, storage, networking, and security systems. 


Following thorough testing and validation, the actual migration of applications, data, and workloads to your new cloud environment can take place. 

There are several strategies that you can use to accomplish this, including:

  • Rehosting—moving applications to the new system as they are.
  • Replatforming—modifying applications slightly for the new system.
  • Refactoring—completely rewriting applications for a modern, cloud-native environment.

Choose the best cloud migration strategy for your business by considering the knowledge you have of your current system as well as your future goals.

Legacy system migration best practices can help you access the benefits of new technologies

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Consider an organizational change management (OCM) strategy

Projects like mainframe application modernization involve huge changes to a company, but an organizational change management (OCM) plan can help make the transition smoother.

OCM covers the planning, implementing, and managing of changes as a business moves to a new process or strategy. It includes planning changes, getting buy-in from employees, and working together for implementation.

OCM can be broken down into multiple different processes, some of which can include:

  • Planning—identifying the need for change, setting clear objectives, and developing a plan. This phase should also involve defining the roles and responsibilities for managing the process.
  • Communication—clearly conveys the reasons for the change, its benefits, and the impacts on individuals and teams. No change in a company will be effective without buy-in from management as well as ground-level staff.
  • Implementation—executing the change plan, monitoring progress, and making adjustments as needed. This might involve training employees on the new system or processes, which is especially important if you’re replacing an old software entirely.
  • Evaluation—adjusting to the change once it's made is as important as making it. A good change management process ends with successive rounds of testing, validation, reviewing KPIs, and gathering feedback to perfect the implementation.

Hire the right people and services to conduct your migration

Different migration and modernization projects will have wildly different needs, so there’s no one-size-fits-all solution. 

For example, OpenLegacy’s hybrid cloud integration can bridge the gap between legacy systems and a modern cloud solution. This means you avoid the money, time, and headaches of a full migration while being able to enjoy the benefits of a highly automated cloud environment.

Continue testing and validation process post-migration

People in change management emphasize the importance of monitoring and evaluating change after completing the migration of legacy systems. You don’t know whether it will be successful until it’s in action, so you need to know how to measure success and act on any feedback.

In software, this might mean breaking a big system down into self-contained microservices. Microservices allow each business function to run on an isolated system, making it easier to test them and verify that your system works the way you think it does. You can also get much simpler, clearer analytics related to each business function, which lets you relate your small-scale software analytics back to your overarching business goals and KPIs.

Get your ROI faster—migrate with OpenLegacy 

No matter your modernization needs, OpenLegacy is the best way to achieve legacy system migration best practices. Our hybrid cloud solution has a three-step onboarding process that helps our customers achieve a 10x faster time-to-market. 

OpenLegacy Hub also offers a flexible “API Factory”, which allows you to create the services you need to access your new system. Plus, our instant integration options mean you can access the data your business relies on from whichever modern app or service is best for you.


FAQs about legacy system migration best practices

What are the “three Rs” of a migration strategy?

The “three Rs” of legacy migration strategy are rehosting, replatforming, and refactoring. 

These are three different ways of migrating a system. Rehosting (or “lift-and-shift”) moves the entire system to a new server or cloud platform. Replatforming involves software engineers making changes to a system to improve performance, reliability, and maintenance. Refactoring sees larger changes made to the codebase, potentially up to a total rewrite.

Each method has unique benefits and drawbacks, and the best strategy for you will depend on your business needs.

How is it best to extract data from legacy systems?

There are many ways to extract data from legacy systems, but, any migration or modernization project will come with certain costs, risks, and challenges.

OpenLegacy offers a hybrid cloud integration solution for legacy application modernization. This allows you to keep accessing your legacy system applications and data while taking advantage of the latest user-friendly software.

A hybrid solution also keeps your options open. With OpenLegacy’s flexible, future-proof platform, you can integrate your legacy systems and use them for as long as it makes sense. You’re also better prepared for a full migration if it becomes more valuable in the future.

What are the best techniques to deal with legacy systems?

When dealing with legacy systems, it’s critical to get it right. For example, an insurance legacy system transformation will involve complex and sensitive financial information. To make sure migration goes smoothly you should prioritize documentation and knowledge management, incremental modernization, and testing and validation for quality assurance.

A thorough inspection of legacy systems increases understanding, putting you in a better position for using as well as modernizing it. With better knowledge of your system, you can identify code that’s causing problems and refactor it to increase stability, efficiency, and security. Incremental refactoring and modernization allow you to improve legacy systems while continuing to use them.

Quality assurance supports incremental modernization and system documentation as testing and validation can highlight issues and ensure that your system works as expected now and in the future.

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