Why & How to Migrate a Legacy Application: Benefits, Challenges, How to Do It & More

Choosing to migrate a legacy application is no small decision. Enterprises typically become dependent on essential legacy systems, making the thought of moving away from them a daunting one. It’s something, however, that many businesses have to consider if they wish to scale and evolve with the times. 

Legacy application systems built with older program languages like COBOL or RPG are becoming increasingly more difficult to maintain and manage. They also don’t easily connect with the kinds of modern technologies organizations must leverage to remain competitive. 

Finding a way to move on from such legacy systems is what drives many enterprises towards legacy application migration. However, while migration can help businesses improve customer experience, adapt to new technologies, and tackle industry challenges, it is only one of the paths to digital modernization and is not a one size fits all approach.

Depending on your business needs, a hybrid integration strategy, which allows you to continue using critical capabilities and benefit from cloud services without committing to a full migration, may be a better choice.

Whichever way you choose to go, a fuller understanding of migrating legacy applications, why you may choose to do so, and the challenges you may face will help you on your way. That’s just what you’ll get by reading on. 

What is legacy application migration?

Legacy application migration is the process of relocating a legacy system or application to a more modern environment. Typically, that means migrating an on-premises application into a secure cloud environment. 

There are many reasons why you may want to migrate a legacy application, and we’ll get into those shortly. First, though, it’s worth making clear what we mean by a legacy application. 

Whereas some describe legacy systems as, by nature, outdated or even obsolete, we’re not following that definition. Rather, by legacy applications we mean those that rely on older technology and exist in older environments. It’s a nuanced but important distinction, as those applications can still be useful, and in fact, critical to your business while still needing modernization to make them more future-proof and fit for purpose moving forward. 

With the what of legacy applications and legacy application migration out of the way, let’s dig down into the why. 

Why migrate legacy applications?

Legacy systems and applications can inhibit business growth potential and pose risks to productivity, adaptability, and security. Recent research from Statista reveals that factors such as increased security, improved efficiency, and cost reduction are the main drivers behind legacy applications migration and modernization:

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Businesses often use legacy applications for many years before recognizing the dangers and modernizing to newer technologies. It could be a legacy core system (transaction servers such as Mainframe or IBM i / AS400), ERP (Enterprise Resource Planning) system, CRM (Customer Relationship Management) software, or accounting program that’s the problem.

Regardless of type, migrating your legacy applications to newer platforms—or otherwise modernizing your systems— can breathe new life into your business, whereas maintaining outdated software may mean wasting resources on things like upgrades to fix compatibility problems.

These issues can increase costs and put your business at a disadvantage relative to competitors, ultimately stopping you from reaching your full potential. That’s why it’s crucial that businesses prioritize legacy migration.

Organizations using legacy systems need to consider the fluid nature of consumer behavior and adopt efficient systems and technology as business dynamics continue to evolve.

The key advantages of legacy system application migration are improved system performance, enhanced security and compliance, and reduced business expenditure:

Improved system performance

Aging legacy systems can damage efficiency and productivity. By investing in legacy application migration, however, businesses can leverage cutting-edge software and technology, boosting processing speeds and overall system performance.

Enhanced security and compliance

Legacy systems often no longer have developer support or up-to-date security measures, leaving them at greater risk of cyberattacks and security threats. By moving to a modern system, businesses can take advantage of stronger security protocols and features to safeguard their data and applications.

Reduced business expenditure

Older systems can be costly due to the complexity and specialized knowledge (such as familiarity with COBOL) required to keep them operational. By moving to a newer platform, businesses can utilize new development tools and processes, streamline IT infrastructure, and prioritize other pressing business needs.

In addition to the above benefits, migrating legacy software can also help you achieve the following for your business:

• Seamless integration. A modern platform supports seamless integration for business applications, helping you streamline workflows and foster better collaboration between departments.
• Exciting new features and better functionality. Migrating legacy systems often means gaining access to exciting features, which can boost functionality. This helps businesses thrive in competitive marketplaces and adapt to changing business needs.
• Better scalability. Legacy systems may struggle to accommodate the workload as your business expands over time. Modern environments offer scalable technologies, such as cloud-based services that support expansion and sustained growth.
• A memorable user experience. New features and functionality provide a more rewarding user experience, which can significantly improve your productivity levels.

Overall, legacy system application migration helps organizations stay ahead of the competition and reduces the burden of maintaining outdated systems.

How to migrate legacy applications: The most common approaches

Once you’ve decided that you may need to migrate or modernize a legacy application, the question becomes how you can do it. In truth, there’s no one-size-fits-all approach to legacy application migration, and the path your enterprise should take will depend on your unique needs. 

There are, however, three common types of legacy migration—and a fourth, more innovative approach, that’s well worth considering:

Rehosting

Rehosting, commonly known as "lift and shift," is a method for legacy application migration to the cloud that doesn’t involve modifications to the source code or underlying architecture of the program. 

Using a rehosting strategy means creating a virtual machine or container with the necessary software to operate the legacy application in the cloud—including the database, middleware, and operating system. This method is typically employed for migrating large-scale applications used in accomplishing critical business objectives, such as a rapid product rollout or vacating a physical data center.

Here are some benefits of rehosting:

• Cost-effective. Rehosting can save you money by allowing you to move your legacy apps with few modifications to their code or architecture.
• Migration speed. As rehosting doesn't require major changes to the source code of the targeted apps, it's a good option for swift migration.
• Low risk. Since the application isn’t changed during the rehosting process, the associated risk is low. Errors and service interruptions can be avoided as a result.
• Improved performance. When rehosted in a modern environment designed for scalability and performance, the performance of legacy applications can be significantly enhanced.
• Better security. Rehosting legacy applications in secure environments that are built to prevent cyber attacks and data breaches is an excellent way to boost security.

However, rehosting is not without potential drawbacks. Due to the lack of changes made to applications during migration, they may not perform as well as they could.

The challenges of integrating legacy applications with cutting-edge cloud services may also remain. This might cause problems with performance or prevent you from benefitting from cloud-native tools and services. To guarantee that the rehosted application continues to function properly, it may also still need regular maintenance and management.

Refactoring

Refactoring involves making changes to the app's code and architecture to migrate legacy system applications to the cloud. This method allows businesses to restructure their applications for optimal performance and make full use of the flexibility, scalability, and cost-saving features of cloud services.

Here are some of the key benefits of refactoring for legacy system application migration:

• Better performance and scalability. Refactoring helps businesses rebuild their applications to take advantage of cloud-native capabilities and services, which improves both performance and scalability.
• More flexibility. Legacy applications can be made more flexible and adaptive by refactoring since this involves splitting them into smaller, modular components that can be upgraded or modified as needed.
• Better security and compliance. By adopting industry-standard cloud security and compliance policies, refactoring can help businesses boost app security.
• Improved user experience. Refactoring can enhance the user experience by making applications more user-friendly and improving responsiveness.

There are several challenges to consider before choosing a refactoring approach, however. If the application's code is particularly complicated or poorly documented, refactoring can take a long time and cost more. Furthermore, this method can be high-risk— if not conducted correctly, refactoring operations can lead to significant downtime or data loss.

That said, refactoring could be a good choice for businesses that want to leverage the full power of cloud-based services and are in a position to dedicate the necessary time and resources to modifying their applications.

Replatforming

Replatforming is perhaps best described as a mid-way point between rehosting and refactoring. It involves making minimal changes to an application in order to move it to a new platform—typically from an on-premises environment into the cloud. That’s as opposed to rehosting which makes no changes and refactoring that makes significant changes to code and architecture.

A replatforming approach aims to preserve the central functionality of the legacy application while still leaving room to benefit from modern infrastructure benefits. For example, perhaps a manufacturing firm runs their Enterprise Resource Planning (ERP) solution on on-premises infrastructure. They might choose to replatform it to a cloud environment to make it easier to integrate with other solutions without losing its business-critical functionality. 

Here are some of the benefits of replatforming for legacy application migration:

• Improved performance - The minor changes to code and architecture can boost the efficiency of the application and open it up to more modern technology. 

• Scalability - Replatforming to a cloud environment introduces the benefit of easier scalability that comes as standard with that kind of environment. 
• Speed and ease of implementation - Unlike refactoring, the changes made to the application when replatforming are simpler to complete. This makes it a faster and easier to implement approach. As mentioned earlier, it’s essentially a mid-way alternative between rehosting and refactoring.

There are still some challenges to consider in the case of replatforming, however. Most notably, it may not fully address the underlying issues with the legacy application. For example, you may still be left with some outdated code or complex dependencies. 

Or, take a hybrid integration approach

The above are what you might call the three traditional approaches to legacy application migration. Another, more innovative approach, may be to decide that modernization rather than migration is your best course of action. A hybrid integration approach, like that you can take using OpenLegacy Hub, can help you strike the ideal balance between legacy systems and modern applications. 

Rather than rehost, refactor, or replatform, hybrid integration means you expose whatever legacy assets or data you need, when you need, without risk to regulatory compliance or business continuity because no changes are made to your legacy system. It can provide either a real alternative to legacy application migration or a way to perform that migration on your own terms and to your own timeframe. 

Here are some benefits of hybrid integration:

• Less complexity - You can automate access to legacy systems and instantly generate cloud-native services with little expertise necessary from your side. 

• Time- and cost-savings - As you don’t need any legacy skills and a choice of no, low, or full code options, hybrid integration can save both time and money as compared to traditional migration strategies.

• Reduced risk - Mission critical systems are kept stable and operational, but simply also opened up to the benefits of a cloud environment. 

Legacy application migration challenges to consider

Of course, legacy application migration isn’t entirely straightforward or without its challenges. If it was, there wouldn’t be such a gulf between the number of professionals who understand its importance and those who believe their organizations are already on top of things. 

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A recent report from IBM demonstrates precisely what we mean by that. While 83% of those asked agreed on the central role of modernizing applications, only 27% said that their organizations had actually modernized many workflows. 

The following are some of the main types of challenges that hold some enterprises back, and which you’ll need to understand to make your legacy application migration strategy a success:

Technical challenges

Increasing the reliability and performance of your applications should be one of the main aims when you decide to upgrade to a modern environment. Keep in mind, though, that legacy software can be bulky. As a result, it's likely that you'll lose certain features and functions that previously influenced the performance of the application.

Some legacy applications may also be incompatible with modern cloud servers since they were developed using outdated technologies. Significant changes to the application's code are one solution to such cases, however, this can make the process longer and more expensive.

Another solution for systems or applications that cannot be migrated is hybrid integration. This method connects on-premises infrastructure with cloud-based services, allowing businesses to maintain existing critical capabilities while selectively adopting cloud-native services for their benefits.

Hybrid integration acts as a catalyst for digital transformation and is an alternative to complete migration. As a modernization strategy, it allows companies to preserve valuable investments, critical functionalities, hard-to-access data, and essential processes while leveraging the scalability, flexibility, and cost-efficiency offered by the cloud.

Risks of project delays and cost overruns

Legacy modernization projects can be a handful. You might need to transfer large data volumes found in legacy systems to the new environment. Data migration in such cases is a challenging procedure that has to be well-planned to avoid data loss or corruption.

Besides this, you might also have financial limitations that require close attention, since uncertainty about the migration project's scope early on and inaccurate budgeting can lead to cost overruns later on.

In reality, you might need to spend more than initially allotted. So, you need to leave room in your budget for any additional, unexpected expenses that may arise as you attempt to resolve issues, transition to modern technology, or scale your teams.

Security and compliance risks

It’s possible that your legacy programs were built with outdated security features and haven’t been upgraded to account for modern threats. Moving these applications to the cloud can actually increase the likelihood of security issues, cyberattacks, or data leaks.

It might also be difficult to get the necessary in-house expertise to configure cloud infrastructures for older applications. Vulnerabilities and compliance issues might occur if the system isn’t properly set up.

It's also important to remember that there are some security concerns unique to the cloud that may not be present in legacy systems.

That said, the risks associated with transferring legacy apps to the cloud can be managed with proper planning and the assistance of cloud service providers with experience in this area.

It’s essential to conduct in-depth security and compliance evaluations before and after the transfer to locate any weak points and guarantee that the application complies with all applicable industry standards.

A four-step process for migrating legacy applications

There are several legacy application migration best practices to follow to give yourself the best chance of success. We’ve distilled them down into a three-step process involving an examination of your existing system, the creation of a migration strategy, and testing of the new environment using a phased approach:

Conduct a thorough analysis of existing applications

Successful legacy application migration requires careful analysis of the current application landscape. You must assess all your apps to see which ones need to be transferred.

This process should include finding out what makes up an application, how it works, and what its performance and scalability needs are. After doing this, you can better anticipate and prepare for any problems that could arise during the migration process.

Determine if the apps' supporting infrastructure can be moved to the cloud, and then create a migration strategy complete with resources, timelines, and budgets. Risk analysis and backup plans should be put in place to tackle any problems that arise during the migration.

Choose the right migration strategy and technology

Determine if rehosting, refactoring, replatforming, or a hybrid integration approach is the best migration strategy based on your examination of the existing applications. 

Each approach has its pros and cons, so your choice needs to depend on the complexity of your application, your business needs, and the timeframe available to you for your migration or modernization. Explore the options available to you, and select the one that best serves your business. This involves thinking about things like security, scalability, and price.

Develop a comprehensive testing plan

Do a practice migration to ensure a smooth transition when it’s time for the real deal. During a test migration, you can run the app in a setting that closely mimics real-world situations.

The purpose of the test is to eliminate any bugs in the system and gain insight into how users will engage with the new environment before the full rollout. These tests can be time-consuming, as they require users to evaluate the application in real-world scenarios. Despite the time commitment, however, this remains a low-risk strategy for finding problems ahead of time.

When the migration is complete, test the application extensively to confirm it’s performing as expected and continues to fulfill the needs of the company. Make sure the app is always optimized for the best possible performance in the cloud.

How can OpenLegacy help you modernize or migrate legacy applications?

If you want to keep up with the competition in today's dynamic market, you need to make sure you’re not held back by outdated legacy systems. Not all legacy applications are outmoded or in need of replacement, of course, but all enterprises should have their eyes firmly set on the future.

Modernization projects succeed when they effectively manage risk and maintain continuity.  OpenLegacy Hub and  Decoupling patterns provide a disciplined approach to isolate, migrate, and modernize portions of a legacy system while all the rest continues to operate. 

• Reduce modernization risk by changing one boundary at a time—instead of a “big‑bang” overhaul.
• Deliver incremental ROI as each decoupled component can adopt cloud‑native capabilities immediately.
• Work in parallel streams—modern teams can refactor or rewrite individual services while legacy experts maintain existing operations.
• Future‑proof the architecture by replacing brittle program calls with API contracts that scale, secure, and observe like any modern service.

OpenLegacy can support your business complete legacy system application migration your way. 

FAQS about legacy application migration

How do I migrate legacy systems?

• Determine what information will be transferred to the new platform.
• Find out the money, time, and resources you'll need to migrate.
• Conduct a data backup.
• Develop a migration strategy for your system.
• Test the migration plan.
• Conduct routine maintenance checks.

Ultimately, it’s important to plan, execute, and manage the migration of old systems carefully. Collaboration between business executives, IT teams, and end-users is crucial for a smooth transfer that benefits all parties involved.

What is a legacy system conversion?

The term "legacy system conversion" refers to the process of converting an older system into a new platform that accommodates modern technological features and standards. Existing software, processes, and data repositories must be modified to run on the new system or platform.

Several stages, such as code translation, data mapping, and testing, may be necessary to guarantee that the converted system is up to par with all specifications and performs as intended.

Some of the reasons for converting legacy systems include making them more efficient, cutting down on maintenance costs, and allowing them to be integrated with newer software and hardware.

Businesses can improve their IT infrastructure, increase application longevity, and reduce operational disruptions by modernizing their outdated systems.

What are examples of legacy applications?

Legacy applications are crucial to business operations but were built using outdated technology. Mainframe software is one such example. These centralized, enterprise-level systems were designed to handle vast volumes of data and first emerged in the 1960s and 1970s. Today, they’d be prime candidates for legacy application migration or modernization.