Which layered architecture pattern is commonly applied when refactoring a monolithic COBOL application?

Think of it like working hands-on with IBM mainframe systems — the answer here is 'Combining all COBOL programs into a single layer to reduce inter-program CALL overhead'. A layered architecture separates CICS BMS presentation, COBOL business logic, and DB2 data access into distinct layers, providing clear boundaries and enabling independent modernization of each layer. On real mainframe exams, this concept comes up repeatedly so make sure you have it locked in.