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Moving Mainframe Apps to the Cloud: Should You Stay or Should You Go?

Over the last few years there’s been a noticeable push from the big public cloud data center providers to encourage enterprises to move their zSystems mainframe applications to the cloud.

Cloud providers are offering a mix of support to entice companies, including development and runtime environments, systems integration tools and expertise—plus assurances that moving to the cloud is straightforward. Two main alternatives are available, the simplest being to keep existing zSystems applications essentially as they are, applying only minimal essential changes such as recompiling a COBOL application so it can run on z/OS in the cloud. The second alternative is to modernize and rearchitect the application so that it runs like a cloud-native application. This involves more effort and more risk, as you are making far more significant changes.
But should you embark on an exercise like this at all? Here are five questions to consider first.

1. How fast do you need to process your transactions?

Large enterprises like banks, airlines and government agencies rely on the zSystems platform to process high-volume mission-critical transactions. When computing platforms are compared head-to-head, the latest mainframes such as the IBM z16 are difficult to beat for their combination of sheer power and speed, their reliability and uptime and the high level of security and compliance they can wrap around software systems.

The cloud, built on x86 platforms, might be slowly inching closer to zSystems in areas such as power and scalability, but is probably not yet comparable when it comes to security and reliability. Security on the mainframe is built into every layer of the technology stack, insulating it from attacks. For example, quantum-safe technology, available on the z16, protects data against future attack from quantum computers with the speed and sophistication to “break down” encryption keys produced using encryption standards that are widely used today.

2. Do you have all the right information to make an objective decision?

It’s important to tread cautiously, looking at all the evidence on both sides before deciding if the public cloud is going to be a better fit to run your mission-critical systems.

Objectivity is crucial. What positive benefits do you expect from moving your zSystems workloads? Don’t be swayed by opinions either way, whether it’s the “cloud is best” mantra on one side, or passionate pro-mainframers arguing against moving off the platform at all costs, on the other.

Any strategy that involves moving applications off the mainframe must be based on a cold, hard assessment of what is best for your business—both now and in the long run.

Evaluate how your existing systems and platforms contribute to the efficient running of your organization today, and how they will need to change to support your business processes as they evolve over time. Analyze key metrics from your IT environment, such as transaction volumes, database growth and service-level agreements for customer-facing applications. By mapping these to your longer-term goals, you can start to compare the impact on performance and resources of either staying with zSystems or switching to the cloud. The real goal, as always, is to match the technology to the business process, not the other way around.

Importantly, if your decision is driven by cost, consider the total cost of ownership of various platforms including the public cloud and compare the outlay for running your core transaction-intensive workloads. Bear in mind that escalation of cloud costs will be down to volumes, which may be hard to predict, and rates charged by the cloud vendors, which are likely to increase over time. Also expect to pay more to a cloud provider for “extras” such as keeping your data within the EU in order to comply with GDPR requirements. Some enterprises are finding that the bills for running their applications on the cloud are higher than they expected and are starting to shift some systems back on premises.

3. Are you clear on the risks of migrating critical systems?

It hardly needs saying that critical business applications cannot be allowed to fail during or after the move to the cloud. You must have total confidence that any move can be completed successfully without any hitches, while continuing to meet your service-level targets.

The truth is that cloud providers tend to underestimate the risks when it comes to moving off the mainframe. In practice there is often a complex array of interrelated applications and subsystems to deal with, which cannot just be lifted and shifted to the cloud. A COBOL application could make calls to a Db2 database hosted on the mainframe, or have sub-routines written in a mainframe-specific language such as Assembler, for example. IBM 370 Assembler is tightly tied to the mainframe chip set so it is dangerous to assume that it can port to a different platform.

On top of this, older programs have likely undergone many fixes and changes over the years. These are often poorly documented, making the task even harder.

4. Have you considered modernizing your applications without moving them?

If modernizing your zSystems applications is your primary objective, there is a lot you can do to modernize in place, which avoids the risks of moving off the zSystems platform.

Mainframe modernization tools allow you to add significant new functionality without changing the legacy code. In effect you are wrapping new technology around an existing application; for example, you can add a completely new interface; modernize the business process by integrating with new applications hosted in the cloud or allow cloud apps to access data hosted on zSystems, all without touching the original mainframe code.

Banks and other large enterprises have been doing this for years to good effect, leaving the mainframe to do what it does best: reliably crunch all of those billions of business-critical transactions. Be sure that the cloud offers a better technical and/or financial solution before ruling out other, potentially less risky and time-consuming alternatives.

5. Could hybrid cloud offer the best of both worlds?

Public cloud offerings may be an obvious choice for some companies, such as SMEs who have modest transaction volumes, or organizations with only a few remaining mainframe applications. But for others, particularly those with large-scale transaction processing systems on zSystems, hybrid cloud will often be the better option.
This approach, strongly advocated by IBM, recognizes that organizations will want to continue running a mix of platforms, at least in the short to medium term. IBM has added a host of technical capabilities, such as containerization, Java/COBOL interoperability and LinuxONE to make the mainframe easier for non-specialists to use in hybrid environments and to simplify integration with new applications in the cloud.

The ability to deploy containers on the z16 platform allows you to use the same orchestration technology across cloud and zSystems and to adopt similar IT tools and processes across mainframe and other platforms. Using containers, for example, you can spin up an instance of CICS on the mainframe, and run a greater range of open-source tools than would be available in a traditional z/OS environment.

Minimizing the need for platform expertise reduces the pressure on mainframe skills and provides greater scope for incorporating zSystems into a multiplatform strategy.

Moving applications off the mainframe is not a panacea, and for companies with large and complex zSystems applications there may be better alternatives. Ultimately it’s important to look beyond the hype and ask: what is the right platform for this use case? For many companies the answer will be a hybrid cloud approach, blending the power and resilience of zSystems with the flexibility of the cloud.