When you first disassemble a module, do not use the SYSPUNCH (SYSPCH for z/VSE) output, but print the SYSPRINT (SYSLST for z/VSE) listing. Use the listing to determine which registers are used as program base registers, their initial values, and their ranges. Make up USING statements for these. Find any places where no instructions should be generated (only constants), and make up data-only statements for these ranges. Find any uninitialized data areas (DS areas), and make up DS statements for these ranges. If you can determine any registers that are bases for areas which can be used for DSECTs, determine the range of valid use, and make up DSECT definitions and USING statements for these. Perform a second disassembly, including the above statements, and creating a source program with the SYSPUNCH (SYSPCH for z/VSE) output.