Mainframes have powered some of the world’s most important IT environments for decades. Even with the rise of newer technologies such as cloud computing, distributed infrastructure, and SaaS, mainframes endure.
Banks still use them to process financial transactions. Insurers rely on them for policy and claims systems. Large organizations, from government agencies to international retailers, run their business-critical applications on mainframe infrastructure.
The question is perhaps: Why stick with technology that has been around for decades when newer alternatives are available?
The short answer is that many mainframes still do exactly what organizations need them to do. For workloads that demand high availability, transaction integrity, security, and scalability, mainframe technology offers capabilities that organizations are reluctant to give up.
What makes a mainframe computer different?
A mainframe is a type of high-performance computer that combines significant processing power with the ability to process large volumes of business transactions and data. These machines are designed to support many users and workloads, with features built around:
- High availability
- Transaction integrity
- Large-scale input/output processing
- Workload isolation
- Security
- Reliability
- Compatibility with enterprise applications
These powerful machines are typically at the heart of an organization’s IT environment, acting as a system of record and running applications that support core business processes. This setup sets them apart from conventional servers designed for much narrower workloads.
For example, an enterprise may run hundreds or thousands of distributed servers alongside a mainframe responsible for some of its most important transaction-intensive applications.
How does a mainframe work?
The key components of mainframe hardware include processing, memory, storage, and input/output resources, all brought together within a single architecture. Each central processing unit (CPU) executes instructions and works alongside these other resources to support the mainframe’s workloads. Logical partitions (LPARs) can divide those resources into separate environments, allowing different operating systems and workloads to run independently.
Mainframes can also use virtualization to create multiple virtual machines, allowing organizations to run additional operating systems and workloads while sharing the same underlying hardware. This setup allows mainframes to support multiple operating systems, databases, transaction environments, and user groups without using separate machines for each workload.
Why do organizations still use mainframe computing?
Mainframes have been around for decades, so it is easy to assume organizations retain them simply because moving away is difficult. That isn’t always the case, though, as many enterprises keep them because they do their job extremely well.
The platform is not simply being maintained either. BMC’s 2025 Mainframe Survey found that 72% of organizations reported growth in general-purpose mainframe capacity.
Reliability and availability
Downtime is a major risk for enterprise systems, with outages causing serious ramifications across the business. For example, if a payment system stops working, customers can’t complete transactions. Or, if a reservation system goes offline, operations grind to a halt.
Mainframes are engineered for environments where uninterrupted operations are a necessity. Built-in redundancy and fault tolerance help keep critical workloads running and reduce the impact of individual system failures.
High-volume and large-scale processing
Mainframes are designed to handle large-scale transaction processing and intensive input/output workloads. Whether it’s a customer making a card payment, a passenger booking a flight, or a bank transferring money between accounts, they can process large numbers of transactions simultaneously while keeping records accurate and consistent.
As workloads grow, organizations can allocate additional resources and increase processing power to accommodate greater demand. This allows mainframes to support large-scale data processing from transaction-intensive applications without disrupting the systems and services that depend on them.
Security and control
Mainframes often act as systems of record, holding authoritative data for areas such as customer accounts, policies, inventory control, and financial operations. Other applications can draw on this mainframe data without users interacting directly with the mainframe itself.
Because these systems support critical business processes and sensitive information, security and control are a priority. Capabilities such as workload isolation, access controls, auditing, and governance help organizations protect systems and maintain oversight over how they are used.
For highly regulated organizations, such as insurance companies and financial institutions, those controls can be an important part of meeting security and compliance requirements.
Established business logic
Legacy mainframe applications are another major reason organizations continue to rely on the platform. A core application may contain many years’ worth of business rules, workflows, integrations, and operational knowledge.
If an organization decides to replace a core application, it has to do far more than move data to a new platform. Teams may need to identify and recreate thousands of dependencies and processes that have evolved over many years.
Some of that logic may be poorly documented, and the people who originally built the system may no longer be available to explain how it all fits together. For organizations that still depend on these applications for critical processes, replacement can carry significant cost and risk.
What can become outdated in a mainframe environment?
Different parts of a mainframe environment can become outdated at different times. An organization may run a modern mainframe while still relying on an application, interface, or access tool introduced many years ago.
When problems around access, usability, or integration arise, the mainframe is only one part of the picture. Organizations may instead need to address:
- The application running on the mainframe
- The interface employees use
- The terminal emulation or access software
- Integration with newer systems
- Endpoint management
- Skills and maintenance requirements
A green-screen interface, for example, does not necessarily mean the underlying platform is obsolete. Modernization is most effective when it targets the parts of the environment that no longer meet the organization’s needs.
The way users access mainframe applications is a good example of how this technology has evolved independently of the mainframe itself.
How are mainframe applications accessed?
Mainframe applications were originally accessed through physical terminals connected to the host. One of the most recognizable examples is the IBM 3270 family, which provided users with a screen and keyboard to work with IBM mainframe applications.
As desktop computing became widespread, physical terminals were gradually replaced by terminal emulation software, which replicates the terminal experience on a modern device. Many mainframe-based applications that use terminal interfaces are still accessed this way, although the way those sessions are delivered has evolved significantly.
Traditional terminal emulators usually require software to be installed on individual endpoints. Modern browser-based terminal emulators remove that requirement, giving users access to host applications through a standard web browser.
Our Jubilant Terminal Emulator, for example, provides browser-based access to IBM mainframe and other host applications without requiring client software, Java, ActiveX, or plugins on the endpoint. You can manage access, host definitions, users, sessions, and settings centrally.
Where mainframe environments create challenges
Even when the mainframe itself continues to perform effectively, the technology surrounding it can become harder to manage over time. Common challenges include maintaining desktop access software, meeting modern security requirements, improving the user experience, and connecting host applications with newer systems.
Desktop software management
Traditional terminal emulation means that IT teams have yet another piece of client software to manage. Each endpoint needs the software to be installed, configured, patched, upgraded, and supported. At enterprise scale, those extra steps add up.
Security and access
Mainframe applications can hold highly sensitive business data, so having tight control over who can connect and how they gain access is important. Modern access requirements are varied, including:
- Encrypted connections
- Multi-factor authentication
- Centralized administration
- Remote access controls
- Support for multiple device types
- Reduced dependence on locally installed software
Organizations need to introduce these controls without disrupting access to the host applications employees rely on.
User experience
Green-screen applications have an unfair reputation for being outdated and difficult to use, even though experienced users can often work with them quickly and efficiently.
That said, problems can appear when organizations onboard new employees, attempt to simplify workflows, support different devices, or make established applications accessible to a wider user base.
If the interface is the problem, organizations can update the presentation layer without changing the workflows underneath.
Integration with modern applications
Integration is another area that can become challenging in a mainframe environment. Many mainframe applications were designed long before REST APIs, SaaS platforms, mobile applications, and cloud services became part of everyday enterprise IT.
The application may still perform its core function effectively, but modern systems need a way to exchange data and functionality with it. An integration layer can give newer applications access to established host data and functionality through modern interfaces and services.
What is mainframe modernization?
Mainframe modernization can take different forms depending on which parts of the host environment no longer meet the organization’s needs. That might mean improving access, modernizing the user interface, connecting legacy systems with newer ones, or moving selected workloads to a different platform.
There are several ways to modernize mainframe applications, depending on whether the priority is access, usability, integration, or the application itself.
| What changes? | |
| Access modernization | How users connect to the existing application |
| UX modernization | How users interact with the application |
| Integration modernization | How the host system connects with other applications |
| Application modernization | How the underlying application is structured or developed |
| Migration | Where the application or workload runs |
The right approach to mainframe modernization depends on what is creating the problem, alongside factors such as risk, cost, skills, application dependencies, and long-term IT strategy.
Modernize the access, not the system that works
Our Enable, Enhance, and Evolve approach maps modernization priorities to three practical ways of working with existing host applications.
- Enable – Jubilant Terminal Emulator gives users browser-based access to mainframe and other host applications without installing client software, plugins, Java, or ActiveX on the endpoint.
- Enhance – Our UX Modernization uses no-code and low-code tools to transform existing terminal screens into modern web interfaces while retaining the host application, business logic, and data underneath.
- Evolve – We can expose host data and functionality through standards-based web services, giving cloud, web, mobile, and other applications a way to work with existing systems of record.
Ready to modernize how your teams access and use existing host applications? Talk to Jubilant about the right approach for your environment.
