The Technical Challenges to Mainframe Modernization

In past articles, we’ve discussed the human/psychological and business obstacles to mainframe modernization. In this article, CloudFrame’s Chief Scientist Balaji Swaminathan delves into the unanticipated technical roadblocks that companies stumble into when attempting modernization. Modernizing legacy systems can be like panning for precious minerals. Some of the stuff you find under the grime can be very surprising.??

Navigating the Maze: Challenges Associated with Mainframe Modernization??

Modernizing mainframes is like renovating an old house—you start with a clear plan, only to uncover hidden issues behind the walls. During my time in this field, I’ve seen firsthand how organizations embark on this journey expecting a straightforward transformation, only to face unexpected roadblocks.?

If you’ve been in the trenches of mainframe modernization like I have, you know this isn’t just about rewriting COBOL into a modern language or moving everything to the cloud in one fell swoop. It’s a complex beast, one that many customers approach with the hope of finding a silver bullet solution. Spoiler alert: there isn’t one.?

Expectation vs. Reality?

I’ve seen companies dream of modernization as a seamless transformation—a magical tool that automates everything overnight, making legacy applications cloud-native with zero friction. But reality quickly sets in when they realize the mainframe ecosystem is not just COBOL/DB2/CICS. There are hidden layers—Assembler, REXX, CLIST—custom-built decades ago and still crucial to operations.??

The Hidden Dependencies Trap?

Then there are the sneaky dependencies. Every time I dive into a mainframe modernization project, I uncover third-party tools woven deep into the application’s DNA—archiving tools, email integrations, data transfer utilities. Even report generation tools like EasyTrieve, Focus, Xgen, and SAS are often overlooked until much later in the project. The problem? These dependencies don’t just disappear when I migrate; they need replacement strategies or alternative integrations.?

SORT-ing Out the Mess?

Another common roadblock is the sheer extent to which IBM utilities like DFSORT/SYNCSORT are embedded into business processes. Over the years, developers have relied on these utilities for quick data manipulations and report generation instead of writing COBOL programs. When modernizing, these tools become yet another hurdle—requiring new solutions that replicate their complex functionalities without disrupting workflows.?

The Domino Effect of Inter-Application Dependencies?

Let’s not forget how tightly coupled applications are. You modernize one, only to find it depends on service modules owned by another team still running on the mainframe. Without careful decoupling, you’re left with a half-modernized mess—some parts cloud-native, others still locked in the mainframe world, creating an operational nightmare.?

The Scheduler Blind Spot?

Here’s one that often sneaks up on me: batch job schedulers. Enterprises have relied on Broadcom’s CA7, BMC’s Control-M, and IBM’s Tivoli OPC to orchestrate batch workflows for years. But what happens when I move an application to the cloud while its dependencies still reside on the mainframe? Reconfiguring these schedulers and maintaining job dependencies is a challenge I often see ignored—until the production rollout looms near, and then it’s a fire drill.?

Performance Expectations?

Performance expectations can be another rude awakening. A transformed application should not only work but should do so efficiently. Many products promise seamless migration but introduce performance overheads that hurt scalability. Optimizing the transformed code and ensuring it meets performance benchmarks post-modernization is just as critical as the migration itself.?

Incremental, Not Big Bang?

So how do I navigate this maze? The key is to approach mainframe modernization as an incremental journey rather than an all-at-once migration. By tackling dependencies, hidden utilities, and performance bottlenecks step by step, I can ensure a smoother transition with fewer surprises. That may seem overly simplistic, and that’s because there’s more to it. Incremental modernization won’t help if you don’t have the expertise to recognize and overcome the hurdles. Or if you use a tool created by people who lack sufficient experience and knowlesge to engineer their products to deal with the realities and technical challenges of modernization. My suggestion to those looking to start a modernization project is to look beyond the promises, the glitzy website and slick sales engineers. Look at the people behind the product, the cogs in the machine. Make sure they aren’t too new and shiny. You want them worn, scarred, tarnished and still chugging along, making things happen.??