Lesson 1 of 5
Why dual maintenance
9 min
Contoso Motor Co. chose a system conversion: its SAP ECC 6.0 EHP 8 system will be converted to SAP S/4HANA. The conversion project takes many months. During all that time, ECC production keeps running. Alternators are still built in Detroit and Chicago, invoices still go to Great Lakes Fleet Services, and things still break and need fixing. The business cannot stop changing just because IT is building the new system.
Dual maintenance is the period when the same business has two development streams: the maintenance stream that keeps ECC production running, and the project stream that builds S/4HANA. Every change in the maintenance stream raises a question: does the project need it too? If the answer is yes and nobody acts, the fix that solved a problem in ECC is missing in S/4HANA on go-live day, and the problem comes back.
- Project startProject systems copied from ECCFrom this moment the two streams start to diverge
- Build and testDual maintenance periodECC fixes continue; each must be assessed for the project
- FreezeMaintenance changes restrictedOnly emergency and legal changes in ECC
- CutoverProduction convertedECC maintenance stream ends
- After go-liveTemporary landscape removedOne stream again
Where the risk comes from
The SAP Learning course on system conversion is direct about this: a temporary maintenance landscape keeps production supported on the old release until it is converted, only emergency corrections should be allowed there, and the program should aim to shorten the dual maintenance period and the time between converting the development and production systems. Each month of dual maintenance adds changes that have to be carried across, tested again and tracked.
| Risk | What it looks like at Contoso | Consequence at go-live |
|---|---|---|
| Missed retrofit | A pricing fix for Great Lakes Fleet Services is imported to ECC production but never applied to S/4HANA | The old pricing error returns on day one |
| Overwritten project work | An ECC transport is imported into the S/4HANA project system and overwrites an adapted object | Project code regresses; tests that passed now fail |
| Untested retrofit | A fix is retrofitted but not retested in S/4HANA | The fix behaves differently on the new data model |
| Effort overrun | Hundreds of small ECC changes each need assessment | Developers spend weeks on retrofit instead of build |
The four ways dual maintenance hurts a program.
Who is involved
Notice who is missing from that picture: the ECC support team. They keep production running and raise the changes, but they are not the ones who carry those changes into S/4HANA. That hand-off is exactly where retrofits get lost, so the process must make it automatic rather than relying on the support team to remember to tell the project.
Dual maintenance in greenfield and selective programs
Dual maintenance is sharpest in a conversion, because the project systems start life as copies of ECC and the same objects exist in both tracks. A new implementation has it too, in a different form: the new system does not share objects with ECC, but business rules fixed in ECC (a pricing condition, a tolerance, an output) may need the same correction in the new design. The register and the assessment step apply either way; the retrofit itself is usually a rebuild rather than a transfer.
What would you do?
Grace proposes skipping dual maintenance planning because "the ECC support team will just stop making changes." Production has averaged 60 transports a month for a year. What should Luis say?
- Dual maintenance is the period with two development streams: ECC maintenance and the S/4HANA project.
- Each maintenance change must be assessed: does the project need it too?
- Risks: missed retrofits, overwritten project work, untested retrofits and effort overrun.
- Shorten the period and reduce volume; SAP recommends allowing only emergency corrections in the maintenance landscape.
Check your understanding · not graded
Lesson check
1. A production fix is imported to the old landscape but not retrofitted to the S/4HANA project. Risk at go-live:
2. What does SAP Learning recommend allowing in the temporary maintenance landscape?
3. Why count historical production transports per month?