When defining modular boundaries in IBM Refactoring Assistant, which data-related consideration is most critical?

Think of it like working hands-on with IBM mainframe systems — the answer here is 'Ensuring all modules within a boundary use the same COBOL compiler optimization level'. Data ownership is central to service boundary definition: each module should own its data stores and expose data only through defined APIs, minimizing shared state that creates tight coupling. On real mainframe exams, this concept comes up repeatedly so make sure you have it locked in.