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Legacy applications can open you up to many problems—especially security risks. Learn why (and how) to migrate them and improve your efficiency.


Learn Why We Migrate Legacy Applications

Posted by Angela Davis on July 25, 2023
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Should you migrate your legacy applications and systems? If you’re thinking about doing so, you’re not alone.

In this article, we explore why the benefits of migrating legacy applications make it a popular choice for organizations of all kinds. We’ll also look at some common implementation strategies and set out the migration process step by step to demystify the scope of what’s involved.

What are legacy applications?

Many organizations have applications, systems, or technology that are outdated after years of use. These are commonly referred to as “legacy” programs.

Any kind of tech that’s no longer up to date can fall into this category. It could be something as simple as an application designed for use on an old operating system or, on the other end of the complexity scale, older mainframe-based software and file-based databases, like VSAM, that are badly in need of cloud modernization.

Over time, it becomes necessary to update legacy systems to prevent problems that will crop up more and more regularly. They’ll continue to need to be maintained and those who have the knowledge are getting older and leaving the workforce. In turn, this means it becomes increasingly expensive to keep them running effectively.

Eventually, the issues relating to maintaining old applications become critical. Just like with a leaking roof, you can patch it up for a while, but your ceiling might end up collapsing if you don’t do anything about the cause of the problem. 

A graph showing that respondents most often viewed their legacy operating structure/model as a top-three challenge to digital transformation.Image source

Benefits to migrating legacy applications

When you’re considering a big project, such as migrating legacy applications, it’s reassuring to look at the advantages you can expect to gain from this. So, here are a few of the major benefits of embarking on this kind of upgrade.

Boosts worker productivity

The first benefit to note is that you’ll see a spike in productivity once the migration is complete. There are several reasons for this.

From a practical point of view, your updated system will be more reliable. This means increased operational speeds and improved functionality.

Updated applications are also likely to be much easier to use. They’ll be more efficient and have fewer glitches when running. This means your staff will be able to complete their tasks faster than before. 

It also means that everyone in your organization will be happier—after all, no one enjoys struggling with outdated tech.

Overall customer experience is improved

Your customers will expect you to stay up to date with new innovations in tech. It can become a problem if your competitors are offering services and features that are not present in your applications, as customers are likely to switch to the most convenient provider.

On the other hand, if you can stay ahead of the curve, this means a much-improved customer experience. You’ll be able to offer your clients a higher quality of service, including a smoother and more intuitive user interface as well as automated processes that would have previously been manual.

Enhances security

The migration of legacy systems is one of the most important actions you can take to bolster data security.

As legacy applications are based on outdated tech, they’re likely to have significant security vulnerabilities. Worse, many of these might not yet have even been identified. You may not find them until after an attack happens, at which point you’ll be facing a major headache.

Upgrading to a more modern system solves this problem. Today’s applications incorporate the latest data security protocols, so your information and system remain safe.

The annual number of data compromises and individuals impacted in the United States from 2005 to 2022.

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Provides the capacity to create cloud-native applications

If you’re not taking advantage of all the potential advantages of using cloud-native applications, you’re missing out. You could be enjoying increased flexibility, reduced costs, easy scalability, and the ability to react faster to a rapidly evolving business environment.

Migrating your legacy applications to a more modern implementation makes this possible. You can take your legacy apps, upgrade them with new features, and run them via the cloud. For example, data migration from legacy systems to modern database applications hosted on the cloud can make data retrieval more efficient.

Boosts compatibility

A legacy system migration project is an excellent opportunity for a wide-ranging rethink of your digital resources. When you modernize your applications, this implies new code, new platforms, and new tech. In short, it gives you a chance to perform a functional overhaul of how everything works together.

This updated tech will be able to “talk” to other modern platforms and applications in a much easier way. This means you can benefit from seamless integration across your systems. Your day-to-day operations will become more efficient, which will ready your organization to respond quickly as business needs develop.

Common application migration strategies

There are a number of approaches you can take to migrate legacy applications. The best one to choose will largely depend on your business goals.

 Advantages of legacy system migration.

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If you’re looking to rapidly scale up operations, for example, you may need a different method than if your priority is to keep hosting costs low. Here are a few of the most popular application migration strategies.


Replatforming involves moving applications from your existing platform  to the cloud while optimizing for specific functionality at the same time. It may be rather prosaic, but this is also sometimes known as the lift, tinker, and shift approach—which is a pretty good description of what’s happening.

It allows your legacy applications to continue to run in the cloud, so there’s no need to completely overhaul your system architecture. One major upside is its simplicity. You get to keep your legacy applications running but enjoy the benefits of the cloud as well.


Rehosting is similar to re-platforming, but in this case, the legacy applications are switched to being hosted on the cloud with no tweaking. The applications are simply moved, and functional equivalency is maintained. This means users can still access your services while the migration is happening, reducing disruption.

A big advantage of this approach is its speed. As there are no complex optimizations made at the point of switching, implementation is fast and easy. Furthermore, additional changes can be made afterward and are often easier to do once applications are running on the cloud.


There are also situations where you may decide that the existing application needs such an extensive overhaul that you’d be better off with a new one. In this case, you should consider repurchasing, which essentially means replacement.

A good example of this is when a company decides to move to a SaaS-model application. This reduces the burden of managing and maintaining infrastructure and simplifies licensing. 

It may also be a prudent choice from a financial point of view. Accessing applications on a pay-as-you-go basis can be much kinder to an organization’s budget and often makes operations easier to scale as well.


Refactoring, also known as re-architecting, involves moving an application to the cloud while modifying its underlying architecture. You may opt to do this if your initial assessment shows that using certain cloud-native features has become a necessity.

This is often considered to be a modernization strategy instead of a migration strategy. It’s a common approach to mainframe application modernization, for example. It can be beneficial when a legacy mainframe can no longer meet an organization’s business needs or has become too expensive to maintain due to its age.

In some cases, the original source code may not even be available. Re-architecting solves this problem and enables the implementation of cloud-native features to create a more flexible and responsive user experience. A cloud solutions provider like OpenLegacy can help you effectively and securely decommission legacy systems.


If there’s no longer any business need for a particular application, you may choose to retire it instead. In other words, to get rid of it entirely.

While it may seem dramatic, there are a lot of benefits to this approach. Legacy applications running on old versions of an OS can pose a security risk, for one thing. They can also be a drain on business funds. There’s no point paying to maintain an application that isn’t being used anymore.

However, it is essential that you do your due diligence first. Even if an application is no longer being actively used, it may still hold useful data.

A computer screen.
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Finally, you may have some applications that are not ideal for migration. These could be high-risk applications that require detailed assessment before migrating or applications that are only used by a few in-house staff, which would minimize the value of migrating them.

The best strategy in this situation can be to keep the applications within your source architecture.   

Retention can work well alongside a hybrid integration strategy. Hybrid integration gives organizations the ability to connect applications, files, and data across both cloud and on-premises systems. Services such as OpenLegacy can build integrations that provide access to legacy data through the user interface as well as complete green screen transformations to an API.

Using this approach, you can retain or reuse older components within a new, cloud architecture. For some businesses, this can deliver a best-of-both-worlds approach, minimizing the disruption of migrating while delivering the upsides of cloud technologies. 

Legacy applications migration categories

The first step in any migration project is to do a full audit of your organization’s existing systems. This involves mapping out all the products that exist in your stack as well as how they connect to one another.

Once your engineers have a complete understanding of the system architecture, you can begin planning. Depending on your existing situation and project goals, you may choose to implement a full, partial, or phased migration.

Full migration

This involves moving either the full stack or every relevant application at the same time. It’s fast and can save on costs. However, there is a risk of downtime, especially if the applications use large datasets. If there are many users that need to be switched over at once, the transition can be jarring.

Partial migration

There are a number of reasons for choosing a partial migration. In this scenario, data and processes are migrated gradually, which mitigates the risks of migrating everything at once. 

A hybrid integration, where some apps are moved into the cloud and others remain in on-site architecture, is one example of partial migration.

Phased migration

This is the step-by-step approach. Applications and data are moved a little at a time, with a review conducted after each round. Only once all potential issues have been ironed out is the next migration stage started. 

This is often the best choice for migration projects where there’s relatively little time pressure but avoiding downtime is vital. 

Steps to migrate legacy applications successfully

Whichever approach you take to migration, it’s crucial to be methodical. In order to be successful, every project should follow a number of key steps.

Step 1. Establish objectives and a cloud migration plan

The process starts by outlining the goals of your application migration project. This should cover a lot of big-picture ground. You need to have a good understanding of what the purpose of your project is, as well as why and how it will align with your organization’s business objectives.

This is also where you should start thinking about costs. It’s vital to put together a budget for the project that takes into consideration its expected scope and timeframe. From this, you can generate the foundations of your overall plan, and then delve deeper into the technical details.

The winning recipe for cloud adoption according to a graph from McKinsey & Company.

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Step 2. Define the elements of the migration

Next, carry out a detailed assessment of your existing data architecture and applications. If done well, this can provide a robust foundation for the project, so it’s worth spending the time to get it right. Without a full grasp of where you’re starting from, it’s impossible to make progress.

Specifically, this step involves deciding which aspects of your tech environment will be migrated and which won’t (if any). Identifying these is one of the most important parts of the process. 

Make sure to consider potentially complicating factors, such as application compatibility and whether there needs to be a review of encryption protocols.

Step 3. Select the best cloud computing service provider

The right cloud computing service partner can make a world of difference to the outcome of your migration project. 

Factors to consider include where your applications will be hosted and which mixture of services you require. The degree of integration needed with open-source or on-site tools will play a role too. 

Nearly every organization will be considering its budget as well, so look for a provider with a variety of pricing models to find the best option for you.

Step 4. Consider the potential of the business

By this point, you should have established your business needs and explored the different migration options. Now, it’s time to think about how realistic it is that you’ll be able to pursue your preferred migration model.

Specifically, it’s important to look at whether you have the resources to make it work. After all, there’s no point in embarking on a migration project that can’t be sustained by your organization.

There may be issues around a shortage of staff skills, for example. If you select a migration model that requires expertise you don’t have in-house, that’s a problem.

In this sort of situation, there are two options. Either you bring your staff up to the standard you require, which will involve training or hiring, or you choose a different migration solution altogether.

Both may imply an increase in costs, but pursuing an unrealistic strategy can work out even more expensive in the long run.

Step 5. Implement the migration

The big moment. If you’ve laid the groundwork properly, this step should go smoothly. That’s not to say unexpected issues can’t pop up—it’s just a question of being well enough prepared to be ready for them.

The biggest challenge here is minimizing disruption to your operations as the changeover happens. Any downtime can cost your business money and customer satisfaction, so it’s vital to avoid it if possible. 

Another key point is that it’s necessary to synchronize any changes made to the source data while the migration is being implemented. A good application migration service provider will be able to provide tools that can help with this.

Step 6. Assess the success of the migration

Once the migration is complete, it’s crucial to verify everything is working as it should be. Carry out checks on data integrity and make sure all your data is present and correct. You should also ensure all your applications are functioning correctly and measure any downtime that has occurred.

If you find a problem, don’t worry. Migrating legacy applications is a complex business, and it’s rare for everything to go perfectly the first time. The point of this step is to discover where there might be gaps or inadequacies in the system so that they can be put right.

Your migration solution provider will be used to dealing with these sorts of issues. That means they will have years of experience in sorting out problems post-migration. They’ll be able to help you solve them as efficiently as possible.

Project planning.

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Migrate your business’s legacy applications successfully with OpenLegacy

Migrating your legacy applications is one of the most important steps you can take toward modernization. Implementing an effective migration strategy will make your systems more efficient, increase productivity, and enable your organization to respond more quickly to new challenges in a fast-moving business environment.

Incorporating cloud-native elements can unleash innovation and help you deliver the high-quality modern services your customers expect and deserve. Improved efficiencies across the board can also lead to substantial cost savings, while your staff can enjoy a smoother experience when using your applications.

All it takes to reap the benefits of this process are the right partners. With OpenLegacy Hub, you can automate integration and achieve modernization faster.

This unique, cloud-native platform gives you the support you need every step of the way. It provides automated access to any core or legacy system, so you can implement the best solution for your organization.



FAQS on migrating legacy applications

Are legacy systems outdated?

By definition, legacy systems have been around for a long time. It’s inevitable that as technology develops, older systems gradually become obsolete.

However, it’s not always obvious when to retire these systems. That’s because they’re usually still in use to a greater or lesser degree. After all, change is a challenge for most of us. If the familiar applications we use day-to-day seem to be functioning acceptably, we’re likely to be happy to continue using them.

The trouble is that the outdated nature of legacy systems will lead to problems occurring. Worse, these can be difficult to notice at first, especially if they don’t seem to be affecting everyday operations in an obvious way.

In the end, though, it always makes sense to either adapt or overhaul legacy systems. There comes a point where the risks involved in not making a change become too great. You don’t want to wait until then to implement your migration strategy. It’s better to stay ahead of the curve.

What are the risks of legacy systems?

There are several risks posed by legacy systems. These include the potential for spiraling maintenance costs, as well as the possibility that everyone who understands the source code will retire without replacements.

However, the biggest problem is one of the most critical faced by organizations across the globe: cybersecurity risk.

The reality is that legacy systems create security vulnerabilities in several ways.

  • Outdated security features. The system itself was developed before the nature of the security threat changed. It may not be compatible with modern-day cybersecurity best practices.
  • Legacy dependencies. A legacy application may depend on database structures, old software, or outdated operating systems to keep functioning. These can introduce their own security vulnerabilities.
  • Lack of full-stack security visibility. Old code or tools may not be visible to the IT inventory but could cause problems behind the scenes.
  • Internal applications become more vulnerable over time. In the wake of years’ worth of corporate restructuring, some hardware and software that should be removed aren’t and go on operating quietly in the background. Problems can suddenly show themselves when there’s a trigger event like a full IT review.
  • Can’t be changed quickly. Legacy applications might not be able to implement new security layers fast enough.

Why is it important to maintain legacy software systems?

Given the potential problems with security, full and regular maintenance of legacy systems is essential. If there’s a security breach, it can have a massive impact on the reputation of your business—for the worse.

Eventually, it will become ever more difficult and expensive to maintain. At that point, the choice to migrate legacy applications becomes an easy decision.

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