Lesson 1 of 5
Systems of record
9 min
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Every integration problem eventually becomes an ownership question: which system is allowed to create and change this data, and which systems only receive copies? If the answer is unclear, two systems will update the same customer or price, interfaces will overwrite each other, and reconciliation will become a monthly firefight. Defining systems of record is the first job of integration and data architecture.
Three roles a system can play
| Role | Meaning | Contoso example |
|---|---|---|
| System of record | The authoritative source for a data domain; creates and changes it under governance | SAP S/4HANA for customers, suppliers, materials, prices, open items and the general ledger |
| System of reference (consumer) | Holds a copy for its own use; never the source of truth | The plant MES holds material and order copies; the data warehouse holds history |
| System of engagement | Where users or partners interact; captures requests and hands them to the system of record | The fleet-service customer portal where Great Lakes Fleet Services places orders |
Roles are defined per data domain, not per system. One system can be the record for one domain and a consumer for another.
The definition is per domain, not per application. S/4HANA is Contoso's system of record for customers and materials, but its plant MES is the system of record for machine-level production confirmations before they are summarized and posted to S/4HANA. A good architecture states this per domain and per attribute group where needed, for example "S/4HANA owns the customer's legal data and credit limit; the portal owns the customer's portal login preferences".
Why one owner per domain
A single owner per domain avoids conflicting updates and makes reconciliation possible: you always know which value wins. When two systems can both write, you need conflict rules, version checks and someone to resolve exceptions. SAP's Master Data Integration service documentation calls this a multiwriter scenario and notes that it requires coordination to avoid one client overwriting another's updates; it offers patches and optimistic locking with version IDs to help. Those mechanisms exist because multiple writers are hard, not because they are a good default.
How to decide ownership
- List the data domains: business partner (customer, supplier), material, bill of material, pricing, open items, assets, employees, and so on.
- For each, ask where the data is created, where the business process that depends on it runs, and who is accountable for its quality.
- Prefer the system where the governing process runs. Pricing used in sales orders belongs where orders are priced.
- Name a data owner (a business role, such as Dan for finance master data) and a data steward for each domain.
- Record the decision, its reasons and its consequences, including which interfaces become one-way.
- Is the domain used to execute a core business transaction in S/4HANA (order, purchase, posting)?Yes → S/4HANA is the default system of record · No → next question
- Is there a specialized system whose process creates the data (MES, payroll, e-commerce)?Yes → that system owns it; S/4HANA receives what it needs · No → next question
- Do several systems genuinely need to create the same records?Yes → central governance with one hub, not peer-to-peer updates · No → choose the system closest to the accountable owner
What would you do?
The fleet-service portal team wants to let customers update their own billing addresses in the portal and push them to S/4HANA nightly, while Maria's team also maintains addresses in S/4HANA. What should the architect recommend?
- Define ownership per data domain: system of record, reference copies and systems of engagement.
- One owner per domain avoids conflicting updates and makes reconciliation possible.
- Prefer the system where the governing process runs; name an accountable data owner.
- During transitions, state the date when ownership moves.
Check your understanding · not graded
Lesson check
1. Why define one system of record per data domain?
2. What is a system of engagement?
3. What does SAP's Master Data Integration documentation call several clients writing to the same master data type?
4. At Contoso, which system owns the Wave 2 customers after the load into company code 1910?