For many businesses, it’s common to invest in new technology to increase efficiency, support growth, and keep pace with ever-evolving customer and employee expectations. However, many organizations still rely on systems and applications introduced years—or even decades—ago.
This may look like a manufacturer depending on an IBM i application for production, a logistics company running operations through UNIX software, or a financial institution using a mainframe application for high-volume processing. These older systems remain deeply embedded in the processes that keep businesses running.
These are known as legacy systems, but their age does not make them broken or obsolete. Often, they remain an integral part of the IT environment because they still do exactly what the organization needs.
What is a legacy system?
A legacy system is an older application or IT environment that is used in day-to-day operations, even though certain parts of the technology may no longer meet modern business or IT requirements. While legacy systems may be associated with outdated technology, the underlying application may still perform its core role extremely well.
The term “legacy system” highlights the fact that the technology has been carried forward from an earlier generation of IT, even as newer systems and platforms have been introduced around it. Legacy environments can include older applications, operating systems, platforms, and access technologies such as:
- IBM mainframe applications
- IBM i, iSeries, and AS/400 applications
- UNIX and AIX systems
- VMS and VAX environments
- Pick and MultiValue applications
- Applications accessed through 3270, 5250, VT, or other terminal interfaces
- Bespoke applications developed around an organization’s specific processes
Generally speaking, legacy systems remain in use because they still do their job well. A manufacturer may use the same IBM i production management application for decades if it remains reliable and embedded in everyday operations.
That said, issues often arise around the application rather than with its core function. Access, usability, integration, or security requirements may no longer fit comfortably with the wider IT environment. In those cases, modernizing the surrounding technology may be more practical than replacing the application itself.
Why do organizations still use legacy software?
Legacy does not necessarily mean obsolete. Many older systems endure because they support the core processes, data, and workflows the business still depends on. Replacing them can mean recreating years of accumulated functionality while introducing additional cost, complexity, and risk.
Critical business operations
For many organizations, legacy systems sit at the heart of everyday operations. They are often responsible for managing core business processes such as:
- Customer accounts
- Orders and inventory
- Manufacturing
- Logistics
- Financial transactions
- Reservations
- Policies and claims
- Billing
When software is so deeply embedded in a business that employees, customers, applications, and other processes depend on it, replacing it affects far more than the IT department. It can disrupt workflows, interrupt service delivery, and create knock-on effects across the wider organization.
Years of business logic
Over time, legacy applications can become heavily customized, with business rules, workflows, exceptions, and processes designed around how the organization actually operates. If the organization replaced the legacy system, it would need to migrate the data, integrations, and customizations to the new platform without losing the business logic built up over years of use. That can introduce serious risk.
Poorly documented processes can be missed, hidden dependencies can break, and important functionality can be lost or changed during migration. In some cases, the people who best understand how the system works may no longer be available to explain it.
Proven reliability
Not every business-critical system needs to be state of the art. Many legacy systems remain in place because they have proven reliable over many years. If a system continues to handle the required workloads effectively, there is little value in replacing it simply because newer technology exists.
There are also the potential costs and risks tied to wholesale replacement of a legacy system. For business-critical applications, activities such as data migration, application redevelopment, rebuilding integrations, and user training must all be managed carefully to protect business continuity and avoid disruption.
Where do legacy systems create challenges?
As technology evolves, legacy systems can become harder to fit into modern IT environments, even when their core functions still work well. Organizations may require browser access, centralized management, secure remote working, or support across different devices.
In many cases, the problem with legacy systems isn’t the application itself, but how well it gels with these newer ways of working.
Access and endpoint management
Many legacy applications were originally designed to be accessed through dedicated terminals, such as IBM 3270 terminals, rather than the modern hardware employees use today. Terminal emulation bridges that gap by allowing modern PCs and devices to interact with the legacy application.
The drawback is that traditional terminal emulation adds more client software for IT teams to install, configure, patch, upgrade, and support across every endpoint. Browser-based terminal emulation removes much of that overhead by delivering access through a standard web browser.
Browser-based terminal emulator, such as Jubilant TE, can provide access to Mainframe, IBM i, UNIX, VMS, VAX, Pick, and MultiValue applications without requiring traditional terminal emulation software on each endpoint, while leaving the underlying application unchanged.
User experience
Although they may look dated, traditional terminal interfaces can be very efficient. Experienced users can often work through them very quickly because keyboard shortcuts, function keys, and predictable navigation reduce the need to switch between keyboard and mouse.
That said, legacy systems can present a steeper learning curve, especially for users unfamiliar with their interfaces and navigation. This creates a challenge when onboarding new employees, simplifying complex workflows, supporting different devices, or making the application accessible to more users. In those situations, the presentation layer can be modernized without rebuilding the underlying application.
What many organizations then often do is transform established terminal screens into modern web interfaces while retaining the existing host application, business logic, and data underneath. This can help improve usability while avoiding the complexity of recreating a system that still performs its core role effectively.
Integration with modern applications
Many legacy systems were built around data structures and application architectures that predate REST APIs, SaaS platforms, cloud services, and mobile applications. This creates a challenge because the legacy systems still contain valuable data and functionality, but newer applications need a way to access and use that data and functionality.
So, instead of migrating all of the data into a new system (and taking on the complexity that migration entails), organizations can introduce an integration layer. For example, WS Web Services Generator can connect established host systems with modern applications by making existing data and functionality available through standards-based web services. This allows web, cloud, mobile, and other applications to use legacy system capabilities without rebuilding the underlying application.
Security and specialist skills
Another challenge in legacy environments is managing security vulnerabilities while meeting evolving access requirements. Organizations may now need secure remote access, encrypted connections, centralized administration, and stronger authentication methods that were not part of the original system design.
At the same time, fewer people may specialize in older platforms and programming languages, while long-serving employees with detailed knowledge of the application begin to retire. 70% of leaders surveyed by Kyndryl reported difficulty finding the talent required for mainframe modernization.
With Jubilant TE, you can strengthen legacy access by moving sessions into the browser, reducing reliance on locally installed software, and giving IT teams centralized control over users, connections, and security settings. Our browser-based terminal emulator also supports encrypted connections and modern authentication, while UX modernization can reduce reliance on specialist legacy skills through no-code and low-code tools.
What is legacy system modernization?
As we mentioned earlier, many organizations continue using legacy software systems that still deliver significant value but may not fit neatly into modern IT environments. Legacy system modernization helps legacy and modern systems work together more effectively by improving access, usability, integration, or the underlying application itself.
The good news is that wholesale replacement is not the only route. 52% of organizations surveyed by Ensono are optimizing and extending existing systems rather than replacing them outright, rising to 57% among UK organizations.
There are multiple approaches to legacy system modernization. The right strategy will largely depend on which part of the IT environment is creating limitations.
| Modernization approach | What changes? |
| Access modernization | How users connect to the existing application |
| UX modernization | How users interact with the application |
| Integration modernization | How other systems access its data and functionality |
| Application modernization | How the underlying application is structured or developed |
| Migration or replacement | Where the workload runs or which application performs the function |
Modernization does not have to happen as a single major project. An organization might modernize access first while keeping the existing system in place, then introduce a new interface or integration layer as requirements evolve. Another may prioritize connecting selected functionality to newer applications through web services.
The right sequence depends on where the biggest limitations exist and what the organization needs to achieve.
Focus modernization where it matters
Legacy systems remain important across many industries, but fitting them into modern technologies can create challenges. Legacy modernization can address those gaps without necessarily replacing the systems businesses rely on.
By targeting the areas that no longer meet business needs, legacy modernization can improve access, usability, integration, and security while preserving the applications, data, and business logic that still deliver value.
Jubilant approaches this through Enable, Enhance, and Evolve: enabling modern access to legacy applications, enhancing the user experience, and evolving how those systems connect with modern applications and services.
Talk to Jubilant about the right approach for your systems, or try our terminal emulator for free today!
