When refactoring a COBOL application with both batch and online (CICS) components accessing the same business logic, what is the recommended approach?

Think of it like working hands-on with IBM mainframe systems — the answer here is 'Transform online components first and leave all batch programs unchanged indefinitely'. Extracting shared business logic into a common service eliminates duplication and ensures batch and online callers use the same implementation, reducing inconsistency and simplifying testing. On real mainframe exams, this concept comes up repeatedly so make sure you have it locked in.