Question: What is regression testing as it relates to mainframe cobol and what standard or best practices checklist is available online?
Answer: Regression testing is making sure that everything that worked before the changes still works after the changes. The test plan developed during the design phase of the original project will have identifed a series of tests to be run after the system is written to verify that the completed system works. These same tests plus those required to test any applied enhancements make up your regression test suite that you should run before implementing any changes into the live environment. What language the programs are written in and what platform they run on is irrelevant. Regression testing should be applied to all languages on all platforms.
If you didn't design a proper test plan at the start of the design phase of the original project then you should design one now based on what the programs are supposed to do with various data.
This article written by Stephen Chapman, Felgall Pty Ltd.