Posted by Rick Fowler, TCC Director of Mainframe Managed Services

We have been hearing for years that mainframes are no longer viable platforms for modern computing, however over 70 percent of all financial transactions are still processed by a mainframe application. Durand, D. (2017, April 11). LzLabs: The art of mainframe application ‘re-hosting’. Retrieved from Therefore, the conversation has turned to modernization, rather than elimination of mainframe systems.

In a previous blog post, we examined an article titled “LzLabs: The Art of Mainframe Application ‘Rehosting’” in Computer Weekly magazine in which the rehosting concept is broken down into straightforward stages.

Now let’s look at the benefits of this approach outlined in the article. The article states “Traditionally, the mainframe applications would have to be re-invented before any migration can take place. In an as-is ‘re-hosting’ migration, the applications can be migrated straight away, with no changes to the application code. In essence, the mainframe has been reinvented, but it is operating on modern and open infrastructure – the benefits of which can be achieved immediately.”

The benefits include:

  • “No issues with internal end-users, or with customers due to issues (discrepancies in results, etc.) as a result of re-writing the application code. The consequence of these issues, associated with traditional migrations, is often a cause of distrust emerging against the new system.”
  • “No need for retraining and no loss of productivity by end-users. They can continue with their daily tasks just as before – nothing has changed in terms of daily interactions with the application.”
  • “It’s an efficient way to validate the migration: iso-functionality makes the testing simple to define and validate. Results are either strictly identical or they are not. The approach doesn’t leave room for subjective interpretation, it’s entirely objective.”
  • “It enables easy automation of testing at large scale.”
  • “It solves the first half of the modernisation problem in a short time-frame. The applications have been migrated onto a modern long-term sustainable platform, based on very standard components, and can be operated by Linux sysadmins which are abundantly common in the job market, thus far-easier to recruit than mainframe sysadmins.”
  • “The cost savings presented by modern IT platforms are achieved instantly, before any longer-term application modernisation begins – a quick and highly positive ROI.”

“After the “re-hosting” takes place, applications can begin their modernisation process, using state-of-the-art technology, to rejuvenate the legacy application into a modern one, with a rich web-based interface, accessible through web services, restructured in containerised microservices, etc. It then becomes ideal for inter-operability.”

Clearly, this approach has merit and will continue to be refined as the many industries in which mainframes operate look for ways to become more agile while reducing risk and operating costs.

To learn more about TCC’s Mainframe Managed Services please visit our website


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