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17.9 Coexistence, Cutover & Operations

1. Coexistence is an architecture​

During modernization, the old and new platforms usually coexist.

BW/4HANA --------                  +--> enterprise consumers
BW bridge --------/
                  |
Datasphere -------+

The objective is controlled transition, not accidental duplication.

2. Parallel run​

For critical workloads:

  1. run legacy pipeline,
  2. run target pipeline,
  3. reconcile,
  4. compare performance,
  5. compare semantics,
  6. validate security,
  7. obtain business sign-off,
  8. cut over.

3. Cutover​

Define:

  • freeze window,
  • final delta,
  • reconciliation checkpoint,
  • consumer switch,
  • monitoring window,
  • rollback trigger.

4. Rollback​

Rollback must be possible without corrupting downstream consumers.

Document:

  • previous source,
  • previous semantic model,
  • consumer routing,
  • data state,
  • recovery point.

5. Operations ownership​

Assign:

  • source owner,
  • BW bridge owner,
  • Datasphere owner,
  • semantic owner,
  • security owner,
  • business data owner.

6. Cost and complexity​

Coexistence increases:

  • duplicated pipelines,
  • monitoring,
  • support skills,
  • data copies,
  • licensing/platform considerations.

Therefore every coexistence interface should have a retirement condition.

Exercise​

Design a six-month coexistence plan for Finance reporting.

Define:

  • dual-run period,
  • reconciliation,
  • business sign-off,
  • cutover,
  • rollback,
  • retirement date.