As enterprises pursue digital transformation strategies, most must decide what role legacy applications will play. For some, automating the mainframe is the solution. Others go down the path of legacy modernization, and still others combine automation with modernization. Interest in legacy modernization continues to grow. A recent BMC Mainframe Survey reveals that mainframe modernization is a high priority:

Top three priorities for the mainframe in 2020.

As enterprises increasingly set their sights on legacy application modernization, a critical decision looms: which modernization strategy to embrace? The purpose of this article is not to delve into the various modernization strategies. Excellent coverage on various strategies already exists, such as Mike Benson’s “Revisiting Legacy Modernization” in Enterprise Executive. More great insight comes from the IDC White Paper, “The Quanitified Business Benefits of Modernizing IBM Z and IBM i to Spur Innovation.” Anyone who wishes to understand the nuances of various legacy application modernization will benefit from the insights these resources offer. This article’s purpose is to help position an enterprise for the greatest possible modernization success regardless of which strategy it pursues.

Modernization Drivers

For many enterprises, digital transformation is driving legacy modernization projects. The goal is to leverage digital technology in all areas of a business to gain efficiencies and deliver more value to customers faster. Today’s hybrid IT environments are a manifestation of digital transformation. Hybrid applications are giving enterprises the flexibility and agility they need to align technology infrastructure with business needs.

In many enterprises, legacy mainframe applications are prominent features of the IT landscape. Those who architect and manage hybrid applications need for the legacy application portfolio to fully participate in the hybrid IT strategy. This need almost always leads to a decision-making crossroads: re-platform or modernize the legacy apps in place? A number of factors come into play during this consideration process: cost, skills, complexity, performance, time-to-completion, and risk.

Other legacy modernization drivers can enter the decision mix including the cost and complexity of maintaining legacy applications. Skills shortages are increasingly a concern as well. For some combination of these reasons, many enterprises have embarked on a legacy re-platforming initiative. This journey is almost always arduous and marked with frequent, unexpected barriers to the transition. The HostBridge team knows of more than one enterprise that has spent years to modernize via re-platforming, hundreds of millions of dollars spent, and still no finish line in sight.

A major counter-balance to any of these drivers is the unparalleled performance, scalability, and availability of the IBM System z architecture. It appears the mainframe is in the long-tail of its existence. What was easy to migrate to other platforms has migrated. What is left is difficult and risky to migrate. The clear implication is work that continues to run on the mainframe is mission critical. Many enterprises are unwilling to take the risks of migrating these workloads. Yet it is imperative that they participate effectively in today’s hybrid world. Enterprises have no choice to but to find ways to integrate or modernize legacy applications.

A Better Way to Modernize: via API

Organizations seeking to modernize may find themselves at a crossroads, facing a high-stakes decision: modernize-in-place or re-platform? These choices lead in opposite directions.

The most common modernization strategies lead in opposite directions.

There’s a third option for modernization that doesn’t carry the risks, can occur quickly, and at a fraction of the cost: modernization via API. Modernization via API is an approach that:

• Keeps the core business logic on the mainframe
• Moves the user interface (UI) and presentation to a cloud, web, or mobile platform
• Leverages an API that creates a service layer between the two environments
• Positions the enterprise to modernize-in-place or re-platform later if desired

In a December 2020, blog post, “7 Options to Modernize Legacy Systems,” Gartner refers to this API approach as encapsulation and ranks it the easiest and lowest risk of the seven options.

The modernization via API (encapsulation) strategy works in the following way:

1. The UI and presentation layer move to the platform or environment that best serves users and customers. Often, to the cloud or a mobile app. User interaction emphasizes the user experience via interfaces that follow modern conventions and standards. Users are unaware that a legacy application runs transactions on the backend. UI development occurs independently and without concerns for moving business logic and data to the platform on which the UI runs.
2. UI/legacy application interaction occurs via an API. The cloud or mobile-based UI application simply issues an HTTP request to the service layer on the mainframe, where API fulfillment occurs. Services are written in JavaScript and can incorporate new logic as well as orchestrate complex transaction sequences. The service returns output as JSON, XML, or any other standard format.

This approach allows users and customers to use and get familiar with a UI that stays constant. APIs fulfill transaction requests from backend legacy applications. The legacy portfolio can remain in place indefinitely. Or, the enterprise can re-platform them at a measured pace. Either way, the users are unaffected because the interface remains unchanged.

Advantages of Modernization via API

Using APIs to modernize legacy applications creates a number of advantages.

• Agility: separating the UI from the business logic preserves all options for future modernization efforts. Organizations can still pursue re-platforming, or further modern-in-place. Modernization via API doesn’t burn any modernization bridges. In fact, it better positions an organization for any future modernization strategy it may wish to pursue.
• Cost: developing APIs to business to legacy applications is simple, straightforward, and completes at a fraction of the cost of re-platforming them.
• Evolution: in heterogeneous IT environments that experience rapid changes, using a service layer accessible via an API creates a loose coupling. This gives the freedom for either the UI or the backend business logic application to evolve separately from each other.
• Flexibility: APIs and integration scripts can contain new and additional logic that legacy applications don’t contain. This creates infinite possibilities to do more than simply create an integration path. Developers can embed new functions, checks, and features into APIs without having to know COBOL, and without changing the legacy application.
• Performance: keeping legacy business logic on the mainframe allows transactions to run at the fastest possible speed. This performance advantage translates into a better user and customer experience.
• Reliability: changes made to the legacy application don’t break the integration to the UI, and vice versa. As long as legacy application field names don’t change, the integration continues to work. This allows developers to add functions, fields, and rearrange where they would display on a screen without fear of breaking the integration.
• Risk: backend legacy applications do not have to change, removing concerns about tampering with sometimes decades-old code. The API approach eliminates the risks of rip-and-replace re-platforming efforts.
• Speed: creating APIs and services to make legacy applications available can occur in hours, days, or weeks at most. By contrast re-platforming mission-critical legacy applications often requires months or years.

Perhaps the biggest benefit of modernizing with APIs is the assurance of success: the journey is short, and the way is not steep.

The Way Forward with Legacy Modernization

Today’s mainframe is highly interconnected. It’s common for modernization efforts to fail to account for multitude of interactions that take place with the mainframe. To ensure modernizations go smoothly, follow these steps:

1. Analyze the integrations. Audit the existing interactions that hybrid applications, automations, and macros are having with legacy applications. Integration analytics data allows the IT group to understand all the mainframe interactions. The insights from integration analytics enable prioritization of modernization tasks and simplify the planning process.
2. Create the optimal integration architecture. Having APIs invoke RESTful services is ideal for modernization in today’s heterogeneous IT infrastructure.
3. Fulfill the APIs. Creating services and orchestrating service flows with JavaScript on the mainframe is an excellent way to fulfill modernization APIs.

The HostBridge team provides all the software, tools, processes, training, and services to guide an enterprise on its modernization journey. Building APIs and services for a modernization project is easily accomplished using the HostBridge JavaScript Engine (HB.js). Reach out to HostBridge using the contact information at the bottom of this page to see a demo of using JavaScript to build APIs or to arrange for trial HB.js software for prototyping purposes.