IBM this week announced it will preview a generative artificial intelligence (AI) tool for converting COBOL code running on mainframes into Java. The preview will be available next month during IBM’s TechXchange learning event, IBM said.

Kyle Charlet, CTO for Z software at IBM, said watsonx Code Assistant for Z makes use of large language models (LLMs) that IBM has trained to both convert and optimize Java code for z/OS running on IBM mainframes.

Rather than converting COBOL into Java code line for line, the watsonx Code Assistant for Z improves the syntax of Java code generated using object-oriented techniques, he noted.

IBM’s watsonx.ai code model, which will have knowledge of 115 coding languages, is based on 20 billion parameters that will eventually be applied to other programming languages such as PL/1, added Charlet.

That model is the same core LLM that IBM used to create Red Hat Ansible Lightspeed, a tool to generate code for an IT automation framework that is scheduled for release later this year. In the future, IBM will also most likely employ generative AI to convert REXX code into Ansible code, said Charlet.

IBM expects the final offering will combine generative AI tools with its existing Application Discovery and Delivery Intelligence (ADDI) inventory and analysis tool to streamline the modernization of legacy mainframe applications.

The goal, however, is not to move COBOL applications off the mainframe. Java applications created using watsonx Code Assistant for Z will still call the same data sources, such as an IMS database or CICS transaction processing system, as the original COBOL application.

That approach will make mainframes more accessible to a wider pool of developers that know Java, which should increase the overall pace of innovation for application development, noted Charlet.

There are billions of lines of COBOL code currently running on mainframes that, in one way or another, need to be modernized as the pool of developers that know COBOL continues to shrink. Generative AI will make it easier to quickly assess, update, validate and test code, which should accelerate code conversion efforts that otherwise would take years to complete, said Charlet.

It’s not clear how quickly organizations might move to modernize COBOL applications, but as the time and effort to do so decreases, so should the cost of modernizing legacy code. Most organizations still running z/OS on mainframes are committed to the platform, but if they can transition to Java, the overall cost of building and maintaining mainframe applications should decline.

In the meantime, it’s not likely that AI will replace developers. IBM recommends that developers further optimize the Java code generated by watsonx Code Assistant for Z.

Most developers are already using some form of AI to accelerate application development. The next wave of AI will see more widespread use of LLMs that are optimized for specific tasks and that generate more reliable results. After all, the quality of any output from an AI model is always directly related to the quality of the data used to train it. The narrower the set of vetted data, the more trustworthy the AI becomes—the opportunity for erroneous data to create AI hallucinations is a whole lot less than any general-purpose AI model could achieve with customization.