In this series, Janet Sun explores and dispels numerous myths around the mainframe. Continued from Part 1 and Part 2.

What Do You Lose by Moving Off the Mainframe?


Typically, distributed servers support a single application workload.  How many business applications does a typical company run?  Inventory control, order entry, accounts payable, accounts receivable, HR, shipping, business intelligence, research and development (multiple projects).  How many servers would be necessary to support these applications?

Distributed systems are best at handling known and expected types of work when serving a particular business application.  The mainframe is better at handling different and unexpected types of work when serving various business applications for a large number of users.

Distributed servers are sized for peak demand, and additional server machines are implemented to handle failover, development work, testing, and so forth. Generally much unused capacity exists. Therefore, the average utilization of a distributed server farm is very low, usually in the 5 percent to 25 percent range.

Having this kind of unused or underused performance power and resources is not cost-effective. Dealing with large numbers of servers with low utilization on each one is a situation that most IT executives want to avoid.

The recent trend to virtualize servers, and even the cloud “movement,” can be seen as an attempt to consolidate workloads, thus better utilizing capacity and reducing the number of servers. Essentially, it is trying to take a multitude of individual servers and create one giant “super-server” with sharable resources.

In other words, it is an attempt to duplicate what the mainframe already is, and has been for decades. The difference is with a mainframe you’re not layering yet another technology that has to be managed and can break down at multiple points on top of the one you’re already running.  Also, the mainframe has been optimized for managing multiple disparate workloads.  There are literally decades of hardware and software innovations that were specifically designed and implemented to ensure that the modern mainframe is the best “mixed workload” server on the planet.


With increasing attention on security, it is important to note that the mainframe has the highest server security rating in the industry.  The Evaluation Assurance Level (EAL) of an IT product or system is a numerical grade assigned following the completion of a Common Criteria security evaluation, an international standard in effect since 1999.  IBM mainframes have EAL5+ certification.  What does EAL5+ mean? – “The intent of the higher levels is to provide higher confidence that the system’s principal security features are reliably implemented”.

Security is built into every level of the mainframe’s structure, including the processor, operating system, communications, storage and applications.  Security is accomplished by a combination of software and built-in hardware functions, from identity authentication and access authorization to encryption and centralized key management.  Despite the way Hollywood portrays the mainframe, in reality there has never been a reported incident of a mainframe being hacked or infected by a virus.


The mainframe has a high “Mean Time Between Failure” – in other words how long, on average, before it fails.  For the mainframe, this is measured in decades.  The mainframe has unmatched reliability and security, which contribute to its 99.999 percent availability, commonly called “the five nines,” or high availability.

99.999 percent availability means near continuous operation with unplanned downtime of only 5 minutes over the course of a year. Quick recovery and restoration of service after a fault greatly increase availability.

Next time you are trying to get money out of an ATM, buy stocks, reserve an airline ticket, or pay a bill online, think about how important reliability really is.  How much does an unplanned outage cost?  It depends on the industry, but can certainly be millions of dollars per hour.  And this is not just lost sales and revenue, but also affects company image and reputation.

To enhance this reliability, the mainframe has the concept of non-disruptive hardware and software maintenance and installations. This allows installation and maintenance activities to be performed while the remaining systems continue to process work.

The ability to perform rolling hardware and software maintenance in a non-disruptive manner allows businesses to implement critical business functions and react to rapid growth without affecting availability of business functions.

Mainframe Upgrade

In addition to utilization of distributed servers and storage and workload consolidation, the hardware and maintenance TCO category also includes the reduction of the mainframe net present value costs through trade-in value. With distributed servers, companies often do not consider the asset disposal costs of aging or obsolete equipment.

Growing companies typically receive credit for existing MIPS (i.e. capacity) investments, and a full trade-in value applied to upgrade and grow MIPS.

When companies upgrade to the next generation of distributed systems, the lifetime of the system is typically three to five years, and they must repurchase the existing processor capacity, plus any growth. The long-term TCO implications of this can be significant.

One Reason to Consider

Perhaps one reason that companies are considering moving off of the mainframe is that they don’t want to be held hostage by IBM. That’s where the user community can help. Representing over 1,800 of IBM’s largest customers, SHARE helps ensure that IBM continues to deliver value for the dollars they charge for hardware and software. SHARE also drives requirements into IBM to make mainframe hardware and software more usable and continue delivering return on investment.

Final Thoughts

Even though the mainframe concept dates back to the 1950’s – with the latest generation tracing its roots back to 1964 – it has gone though many significant changes while continuing to support applications that were created decades ago. Today, mainframes support Linux and Java and many significant initiatives including cloud, mobile computing, Big Data, and business analytics. In the past, mainframes were large and had special cooling requirements; today they are not much bigger than a large refrigerator and can run anywhere. Next time you come to a SHARE meeting, look at the mainframe that we run in a hotel ballroom. It will be sitting in an approximately 10×10 corner of one of the exhibit booths.

There are certainly business concerns that should be evaluated (and re-evaluated often) as to choice of computing platform for running today’s businesses.  The choice of using a mainframe is not an either-or proposition.

Mainframes and servers can happily coexist. There is a role for the mainframe and a role for servers. Myths about the usability or viability of the mainframe should be ignored and the business drivers (cost, benefit, and risk) for considering switching technologies need to be carefully considered.

Originally published on the blog.

Janet Sun is Senior Consultant, at Sun Coast, responsible for z/OS storage and cloud portfolios.

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