Legacy System Modernization – Fujitsu Limited and IBM Japan, Ltd. today announced that they will accelerate their collaboration in the field of business system modernization in order to advance enterprise digital transformation and address challenges associated with legacy systems. This comes as part of the collaboration between the two companies announced in September 2025.
Modernization is an essential initiative for driving digital transformation. Achieving successful modernization requires careful consideration of business characteristics, system requirements, and architectural attributes, along with selecting optimal technologies and programming languages. Among the effective approaches are rewriting, which converts existing program languages into those suited for modern environments, and refactoring, which enhances maintainability and scalability through improvements to application structure.
In this collaboration, the companies will expand modernization initiatives centered on rewriting and refactoring. This will be achieved by leveraging Fujitsu’s modernization solution “Fujitsu PROGRESSION”, which automatically converts source code, together with IBM’s AI-powered development partner “IBM Bob.”
The scope includes rewriting COBOL programs running on Fujitsu mainframes and UNIX servers into Java, as well as refactoring after conversion. With Fujitsu providing technical support, IBM Japan will serve as the primary provider of the solution. This collaboration will go beyond simple migration of customer assets to jointly promote modernization that supports digital transformation over the medium to long term.
Background
For many enterprises, COBOL applications running on mainframes and UNIX servers represent critical business assets, embodying years of accumulated business processes and expertise. However, in order to advance digital transformation based on effective data utilization and full-scale adoption of AI, it is essential to redesign these applications into flexible and scalable structures.
At the same time, as Fujitsu has announced its roadmap for the end of sales and maintenance of mainframes and UNIX servers [1], migration to next-generation platforms has become an urgent challenge for enterprises. In addition, the ageing workforce of engineers skilled in legacy technologies and the shortage of such talent have revealed limitations in traditional, labor-intensive development and migration methods in terms of quality, productivity, and timelines.
To address these challenges, Fujitsu and IBM Japan will combine their respective expertise and technologies in modernization to jointly promote initiatives that balance stable system operation with future growth.
Details of the Collaboration
Both companies will expand modernization initiatives centered on rewriting and refactoring. In particular, this collaborative solution will deliver high value in cases where, after analyzing business and system characteristics, conversion to Java is deemed appropriate.
1. High-precision source code conversion with Fujitsu PROGRESSION
At the core of the solution is Fujitsu’s source code conversion solution, Fujitsu PROGRESSION, which rewrites COBOL programs running on Fujitsu mainframes and UNIX servers into languages suited for open environments such as Java. Leveraging Fujitsu’s extensive expertise, the rewriting process maintains consistency in business logic and compatibility with existing specifications, thereby reducing migration risks and enabling reliable system transition. As part of this collaboration, IBM Japan has received systematic skill transfer from Fujitsu regarding Fujitsu PROGRESSION, establishing a framework capable of supporting a wide range of use cases.
2. Modernization support through AI agents
By utilizing IBM Bob, an AI agent-driven enterprise development support platform, the companies will automate code correction and refactoring following COBOL-to-Java conversion. This enables efficient, high-quality execution of traditionally labor-intensive processes such as validation of business logic and testing. In refactoring, adopting structured approaches such as clean architecture—separating application structures by function—is critical. In addition to rewriting, the collaboration will modernize business systems into highly maintainable and scalable application structures that can flexibly accommodate future changes and feature additions, thereby enhancing business value.
Fujitsu is advancing customers’ modernization efforts through AI services such as “Fujitsu Application Transform powered by Fujitsu Kozuchi [2].” Through this collaboration, the two companies will integrate and deepen their solutions and expertise in AI utilization to accelerate the modernization of Fujitsu mainframes and UNIX servers, as well as to drive the modernization of other legacy systems operating in Japan.
IBM Japan, with Fujitsu’s technical support, will provide advanced modernization solutions using rewriting and refactoring. The companies will provide modernization services to next-generation platforms on hybrid-cloud environments that do not depend on specific infrastructure, and that are carefully tailored to each customer’s business characteristics, system requirements, and architecture to best support digital transformation.
By combining their expertise and technologies, they will support the creation of foundations that can flexibly respond to changing business environments and generate sustained value.
Future Plans
By integrating their technologies and expertise, Fujitsu and IBM Japan will deliver innovative and high-quality modernization. Going forward, leveraging insights gained through these initiatives and advanced technologies such as AI, the companies aim to build trust in Japanese society and promote the evolution of system foundations that can flexibly respond to societal change while supporting sustainable development.
For more information visit: global.fujitsu
