Modernizing Legacy ABAP Toward Clean Core with Regression Safety

Keep this: job aid

Legacy ABAP modernization card

• Inventory per extension: objects, entry points, usage, clean core level and cause, owner, existing tests.
• Usage: SCMON in production for 13+ months; rare is not unused; owners confirm; retire after a quiet period.
• Outcomes: retire, replace with standard, refactor in place, wrap, rebuild; or leave as is with tests.
• Refactor when logic is sound; rebuild when design or technology no longer fits; strangler fig for rebuilds.
• Characterize first: record actual behavior with test doubles; compare old and new outputs on the same data.
• Control dates, numbers and row order; raise discovered bugs with the owner; never fix inside a refactor.
• Slices: small, tested, reversible, one release; ride-along, branch by abstraction, switches, parallel runs.
• Finish slices: remove old paths and switches before starting many new ones.
• Metrics: level shift, level D in critical processes, retirements, tested critical extensions, upgrade effort; plus escaped defects and rollbacks.
• Avoid vanity metrics: lines rewritten, apps built, overall coverage percentage.