Mainframe Blog

How to Complete a Successful COBOL Version 5.2 or 6.1 Rollout

3 minute read
Bob Yee, Dave Kartzman

After you’ve migrated your COBOL programs to COBOL Version 5.2 or 6.1, it’s time to begin an initial rollout. As always, be sure to refer to the IBM Migration Guide. Following those guidelines will generally make the migration go more smoothly.

Before you roll out your COBOL Version 5.2 or 6.1 programs, set up some comparative testing. Run the data from the previous COBOL release you were using. Later, when you run your new programs, you can compare them to the old programs. This will help you quantify the benefits of migrating to the new release to business leaders. Every machine cycle saved allows other applications to use those saved cycles for better performance.

Rolling Out Your Programs

Begin your initial COBOL Version 5.2 or 6.1 rollout with one business application and document the migration process. This will serve as a template for subsequent rollouts. During and after the initial rollout, seek feedback that will help you inform other business units on the success and encountered issues of the rollout. Discovering issues early on will make it easier to correct them and adjust your template for later rollouts.

After the initial COBOL Version 5.2 or 6.1 rollout, go back to that comparative testing we talked about for an early idea of potential savings. See what worked and prepare to move forward, but don’t begin rolling out everything.

Only convert those applications that can benefit from the new versions of COBOL. Start with your highly arithmetic, floating-point or complex mathematical applications. These application types will take advantage of the z architecture of COBOL Versions 5.2 and 6.1 and will benefit from higher levels of optimization. If applications do not take advantage of the z architecture extensions, or would not benefit from higher levels of optimization, you should leave them in their current versions of COBOL.

As a side note, for sites with 24/7 CICS regions, replacing PDS with PDSE won’t be easy. What you can do is dynamically insert program objects ahead of your load libraries in the CICS RPL. This will provide a way for you to take advantage of new COBOL Version 5.2 and 6.1 programs for CICS.

Continue this COBOL Version 5.2 or 6.1 rollout path, releasing programs that will benefit from the new COBOL version you’ve decided to go with and testing those against their previous versions to calculate savings.

Reviewing Your COBOL Migration Strategy

Before you roll out, it may be useful to go back and review the steps that you’ve taken. For your convenience, here is a list of things to note, compiled from past blog posts on the subject:

    1. Don’t convert your COBOL programs to Java. This requires sacrificing efficiency for cost saving, and the cost saving you generate will be short-lived and evolve into a series of long-term pitfalls costing you more money.


    1. The first step in a COBOL Version 5.2 or 6.1 migration strategy is roadmap planning. You need to understand your current programs, consider some potentially problematic areas you could happen upon when migrating them, understand your hardware machines, and determine which version of COBOL you’re going to migrate to (there’s an explanation for why you have a choice).


    1. If you have a choice between COBOL versions, which is better? Starting at COBOL Version 6.1 eliminates duplicate compiler upgrades twice, once to 5.2 and again to 6.1. However, by migrating to COBOL Version 5.2 first, you can save costs by leveraging the IBM Enterprise COBOL trials for both 5.2 and 6.1 to gain maximum experience and application comfort before making a formal decision to upgrade.


    1. A large percentage of these migration problems are data related, so thorough testing is crucial to discovering them. The testing you do now will save you from countless hours of debugging, potentially losing revenue and disappointing your customers.


  1. There are several types of performance optimization available in COBOL Versions 5.2 and 6.1, but you may need some guidance on how to identify and use these new COBOL optimization features.

Digital business is driving more mainframe activity. Mainframe shops should optimize their programs so they perform well against the modern demands they face from new and growing digital engagement. The best way to optimize your COBOL programs is to migrate them to COBOL Version 5.2 or 6.1. Good luck along your journey.

Access the 2023 Mainframe Report

The results of the 18th annual BMC Mainframe Survey are in, and the state of the mainframe remains strong. Overall perception of the mainframe is positive, as is the outlook for future growth on the platform, with workloads growing and investment in new technologies and processes increasing.

These postings are my own and do not necessarily represent BMC's position, strategies, or opinion.

See an error or have a suggestion? Please let us know by emailing

Business, Faster than Humanly Possible

BMC works with 86% of the Forbes Global 50 and customers and partners around the world to create their future. With our history of innovation, industry-leading automation, operations, and service management solutions, combined with unmatched flexibility, we help organizations free up time and space to become an Autonomous Digital Enterprise that conquers the opportunities ahead.
Learn more about BMC ›

About the author

Bob Yee

Bob has been programming, designing, developing and managing mainframe projects for the IBM Z since 1970. Bob has performed virtually every function within Technology over the years: Abend-AID development manager, support and maintenance management, developer of new products, beta management, product management and 3rd party technical relationships to name a few. Bob started and has managed Compuware's technical relationship with IBM for over 30 years. Currently, Bob is technical consultant for BMC AMI DevX and has been heavily involved with mainframe modernization projects across the product lines in addition to mainframe consulting for various development and customer support teams.

About the author

Dave Kartzman

Dave Kartzman's almost 50-year IT career includes experience with COBOL dating back to 1973. Over the past several years, Dave has given over 100 presentations of information gathered while helping customers migrate to newer versions of COBOL.