How To Modernise An Old SAP Integration
Mateusz
Are you still relying on an old SAP integration that’s painfully slow and increasingly fragile?
These relics demand constant fixes, block seamless SaaS connectivity, and quietly put your S/4HANA roadmap at risk. What once “worked” now holds the business back.
The fix isn’t just another patch or rewrite. You need a structured modernisation plan that follows a strategic, phased approach.
This starts with a thorough assessment of the current architecture, stabilising the core foundations, and then gradually moving from batch-driven interfaces to real-time APIs and events while enforcing a clean-core strategy and putting proper governance in place.
Done right, this approach improves agility and creates a solid foundation for S/4HANA cloud transitions without disrupting day-to-day operations in the process.
But How Do You Know It’s Time To Modernise Your SAP Integration?
Why is my SAP integration slow or breaking? Why does the system choke on a routine EDI exchange? When you start asking these questions frequently, it usually means your integration architecture is already past its expiry date.
Over time, a pattern of friction starts to appear:
- Your team spends more time keeping integrations alive than improving them
- Simple changes like adding a new field, a new saas connection or a new business rule feel risky
- Jobs, IDocs, or interfaces need manual restarts and reprocessing
- Batch windows and overnight jobs dictate how the business operates
- S/4HANA or cloud plans keep slipping because integrations aren’t ready
- Knowledge lives in tribal memory, not documentation
- Only a few people know how things work, and everyone avoids touching them
- Failures are detected by the business, not by monitoring or alerts
- Workarounds appear: spreadsheets, emails, manual fixes outside SAP
When these signs show up consistently, it’s a strong indication that the integration landscape has reached its limits.
What “Modernising SAP Integration” Really Means
Modernisation does not mean replacing every IDoc, migrating everything to APIs, moving all logic to the cloud, or ripping out PI/PO overnight.
Modernisation is about changing how integrations behave, not just how they’re built. It means making your integrations more reliable and observable, easier to change, upgrade-safe, and aligned with SAP’s new clean-core direction.
Visually, the goal is to move from spaghetti to layers.
| Typical Legacy SAP Integration Landscape | Modernised SAP Integration Landscape |
| Most legacy landscapes look like this: [ SaaS Apps ] [ 3PL / EDI ] [ Data Warehouse ] ↓ ↓ ↓ (Files) (IDocs) (RFCs) ↓ ↓ ↓ +———–[ SAP ECC / S/4 ]————-+ ↓ Custom ABAP | A modernised landscape typically looks like this:
[ External Systems / SaaS ] ↓ (APIs / Events) ↓ +———————————————+ Integration / Orchestration (CPI / iPaaS / BTP / Mule) +———————————————+ ↓ ———————————————– ↓ ↓ ↓ (IDocs) (APIs) (Events) ↓ ↓ ↓ [ ECC ] [ S/4HANA On-Prem ] [S/4HANA Cloud ] |
| Point-to-point connections, Business logic hidden in mappings, Little observability, Tight coupling to SAP internals, and high upgrade risk. When one interface breaks, everything downstream feels it. | SAP is no longer the hub. Integrations are orchestrated centrally. Business logic moves out of interfaces, and SAP systems become consumers and producers, not controllers. |
How Data Flows Change (Before vs After)
Before modernisation, data typically moves in large, infrequent batches, tightly coupled to SAP processing windows and custom logic buried across systems. This makes failures hard to detect, slow to recover from, and risky to change.
After modernisation, data flows become more event-driven and API-led, with clear ownership, real-time or near–real-time propagation, and built-in observability. This leads to faster integrations, easier change management, and far less operational friction across the landscape.
| Before (Legacy) | After (Modernised) |
| External App ↓ Custom Script ↓ PI/PO Mapping (Business Logic) ↓ Custom ABAP ↓ SAP Table | External App ↓ Standard API / Event ↓ Integration Layer ↓ (Validation, Routing, Retry) ↓ SAP Standard Interface |
| Logic spread everywhere, no single source of truth, hard to test and change. | Clear responsibilities, testable components, safe upgrades, and easier onboarding of new systems. |
What’s The Best Way to Modernise Legacy SAP Integrations?
Assess your current landscape, then gradually move from batch-driven interfaces to real-time APIs and events, and enforce a clean-core strategy that decouples custom logic and standardises integrations.
Follow these steps.
Step 1: Start with an Honest Integration Audit
Before touching any code, you need visibility. In most landscapes, integrations have grown organically over 10–15 years, often without a single owner or guiding architecture.
What you typically find includes:
- Point-to-point connections
- Custom ABAP reports
- File drops via FTP or shared folders
- IDocs nobody remembers creating
- Middleware flows with business logic buried inside mappings
A focused integration audit helps answer fundamental questions like:
- What systems actually integrate with SAP today?
- Which technologies are used (IDoc, RFC, SOAP, OData, files)?
- Where does business logic live?
- Which interfaces fail most often?
- Which integrations are business-critical?
- Which ones are considered “too risky to touch”?
This step alone often reveals that a significant portion of interfaces (commonly 30–40% in mature landscapes) don’t require full modernisation. They simply need better monitoring, clearer ownership, or minor stabilisation rather than a rewrite.
The goal of the audit is to assess the current landscape end-to-end. That means mapping all legacy integrations, documenting dependencies, manual processes, and data flows to identify redundancies, fragility, and failure points. Pain levels such as frequent outages, high maintenance effort, or business disruption help prioritise what truly needs attention.
Need help with the Technical Audit of the Integration Architecture? AvoTechs can help.
Step 2: Plan for Cutover and Coexistence Early
One of the most common reasons SAP integration modernisation projects get messy is how change is introduced into a live landscape.
After the audit, you should already be asking: How do we modernise without disrupting the business?
Modern SAP environments rarely allow for “switch it off and replace it” scenarios. Integrations are business-critical, and most need to continue running while new patterns are introduced.
That’s why cutover and coexistence planning is not a “last-mile” activity. If you don’t think about it early, the audit findings don’t translate into a safe execution plan.
Decide early on:
- How legacy and modernised interfaces will run in parallel
- Which systems will be the system of record during transition
- How data consistency is maintained while both paths exist
- When and how old interfaces are safely deprecated
A pragmatic cutover strategy should include:
- Dual-run periods, where old and new integrations operate side by side
- Backward compatibility, so downstream systems aren’t forced to change immediately
- Controlled cutover windows, aligned with business cycles (not technical convenience)
- Clear rollback plans, so failures can be reversed without data loss
This planning prevents the classic failure mode where integrations are technically modernised, but operationally unsafe to switch on. When coexistence is designed upfront, modernisation becomes incremental and reversible.
Step 3: Stabilise Before You Modernise
Most SAP integrations don’t fail because of bad architecture. They fail because of poor operational foundations.
Before redesigning anything, fix the basics that keep integrations reliable day to day:
- Centralised logging across SAP and middleware
- End-to-end correlation IDs for traceability
- Automated retries with idempotency to prevent duplicates
- Dead-letter queues and controlled reprocessing mechanisms
- Alerts tied to business impact (not just technical errors)
Addressing these areas alone can dramatically reduce incidents and manual intervention, often without rewriting a single interface.
This is modernisation too, just not the flashy kind.
Here’s an example of stabilising an SAP Integration (before and after )
Consider a scenario in which an SAP ECC system sends Sales Orders to a SaaS platform via IDocs through middleware. During the month-end, volumes spike, and failures continue to disrupt the operations.
| Before Stabilisation | After Stabilisation (No Rewrite) |
| IDocs are sent asynchronously, but failures are only visible in SAP transaction codes Middleware logs are fragmented and not correlated with SAP document numbers When an IDoc fails, the business discovers it hours later, usually from a missing order Reprocessing requires manual investigation, restarting jobs, and re-running IDocs without knowing if duplicates will be created Month-end spikes cause retries, queue congestion, and occasional data inconsistencies | The interface itself stays the same, and IDocs are still used. What changes is how it’s operated. Centralised logging aggregates SAP IDoc numbers, middleware message IDs, and SaaS transaction IDs End-to-end correlation IDs allow tracing one order across systems in seconds Automated retries are implemented with idempotency, preventing duplicate order creation Failed messages land in a dead-letter queue with controlled, auditable reprocessing Alerts are triggered based on business impact (e.g. “orders not posted in 15 minutes”), not just technical errors Clear ownership is defined: who investigates, who reprocesses, who communicates, etc. |
What changed (and what didn’t)
SAP system, IDoc structure, Business process, and Middleware product remain the same. Only observability, error handling, operational discipline, ownership and accountability changed.
Step 4: Understand Your Target SAP Landscape for Modernisation
Modernisation decisions depend heavily on where you’re going, not just where you are.
Selecting the right platform is a critical decision that can significantly impact your business operations. Choose the platform that can adapt as your business needs evolve and is secure when it comes to handling sensitive business and customer data.
| SAP ECC (Still Very Common) | SAP S/4HANA On-Prem | SAP S/4HANA Cloud (Public Edition) |
ECC landscapes usually rely on:
Modernisation here is about:
You don’t need to “cloud-wash” ECC integrations. You need to make them less fragile. | S/4HANA On-Prem introduces:
Here, modernisation usually means:
You can still use IDocs and RFCs, just more deliberately. | This is where things change the most. Side-by-side extensions, middleware, and SAP BTP become essential. S/4HANA Cloud enforces:
Modernisation here is not optional; it’s mandatory. If your integration depends on Direct table access, Custom ABAP logic or hardcoded assumptions, it simply won’t work in the Cloud. |
Step 5: Rationalise the Integration Stack (Don’t Replace Everything)
A common mistake is trying to standardise on one integration technology. Experienced teams don’t do that. They choose the right tool per use case.
| IDocs | BAPIs / RFCs | OData / APIs | Events (Event Mesh / Business Events) |
| IDocs remain a reliable backbone for many SAP landscapes. They handle legacy-to-SAP links without disruption. They are particularly well-suited for: • High-volume, asynchronous flows • Business documents such as orders, deliveries, and invoices • Loose coupling between systems • Resilient, retry-friendly processing IDocs aren’t “legacy.” Poorly designed IDocs are. | When used deliberately, BAPIs remain a valid and powerful integration option. Best suited for: • Transactional operations • Synchronous processing • Scenarios where SAP business logic must execute immediately Use BAPIs carefully to manage locks and concurrency, handle timeouts explicitly, and avoid chatty, high-frequency calls | APIs enable cleaner, more governable integrations and align well with the modern SAP strategy. They are ideal for: • Modern app integrations • S/4HANA and Cloud scenarios • SAP-to-SaaS connectivity APIs are not always faster, but they’re clearer, more secure, and easier to govern | Events enable decoupled, event-driven architectures. They are well-suited for: Near real-time updates, loose coupling between systems, and Scalable, reactive integration patterns
Not every use case needs events. But when timing matters, they shine. |
Modernisation isn’t about choosing one technology. It’s knowing when each one makes sense, and resisting the urge to over-engineer.
Here’s a simple rule of thumb:
- Need high-volume async documents → IDocs (where supported)
- Need speed and decoupling → Events
- Need transactional SAP execution (ECC/S/4 On-Prem) → BAPIs/RFCs
- Need control + governed contracts (Cloud-ready) → Released APIs
- Need governance + orchestration at scale → SAP BTP Integration Suite (plus API Mgmt/monitoring), It helps orchestrate complex integration flows, provide centralised monitoring and alerting, and scale reliably across hybrid and cloud landscapes.
Step 6: Move Business Logic Out of Interfaces
Many legacy SAP integrations fail not because of connectivity, but because business logic is buried in the wrong places.
Common patterns include:
- Business rules hidden inside mappings
- Middleware scripts behaving like mini applications
- No clear visibility into where decisions are actually made
Over time, this makes integrations fragile, hard to test, and risky to change. Modernisation means shifting toward thin interfaces focused on transport and transformation, explicit, versioned business logic, and Clear ownership of where decisions live
That logic might sit in SAP BTP, Middleware, or the consuming SaaS platform. Wherever it lives, it must be testable, observable, and easy to change without destabilising the integration layer.
Step 7: Make It Clean-Core Friendly
Even if S/4HANA Cloud isn’t on your immediate roadmap, clean-core principles still matter.
In practice, that means:
- Stop using direct table reads as an integration strategy
- Prefer released APIs, CDS views, and business events
- Avoid core modifications for integration logic
- Isolate custom behaviour outside the SAP core
Clean-core means your integrations are adaptable; it’s easier to move to S/4HANA, adopt cloud models, or replace systems without rewriting everything.
Step 8: Modernise in Waves (Not Big Bang)
The most successful modernisation programmes don’t try to change everything at once. They move in deliberate, value-driven waves:
- Wave 1: Observability and operational stability
- Wave 2: Architecture cleanup and decoupling
- Wave 3: Interface modernisation (APIs, events, patterns)
- Wave 4: Optimisation, performance tuning, and governance
Each wave delivers value on its own. This avoids the classic scenario where everything changes, and nothing works.
Step 9: Put Governance in Place (So It Stays Modern)
Modernisation without governance doesn’t last. Well-governed SAP integration landscapes support compliance, auditability, and regulatory requirements.
To keep integrations sustainable, you need clear interface ownership, versioning and deprecation policies, standardised error handling and retry patterns, security and access standards, and regression testing as part of change management.
Without these, today’s modern architecture quickly becomes tomorrow’s legacy.
Final Note
After integration modernisation, teams typically see fewer production incidents, faster recovery when issues occur, smoother SAP upgrades, reduced dependency on tribal knowledge, and quicker onboarding of new partners and customers.
And, most importantly, SAP stops being a bottleneck.
If you’re facing slow, fragile, or hard-to-change SAP integrations, AvoTechs can help. Being the most reliable SAP integration consulting firm in Europe, we help our clients solve SAP integration challenges without headaches.
- If you’re facing performance issues, we conduct a technical audit of your integration architecture and recommend targeted improvements.
- If you need to scale your integrations for growth, we provide architecture reviews and optimisation to ensure your landscape holds up at scale.
- For ongoing maintenance and updates, we offer long-term support with clear SLAs.
For integration packages or enquiries, please get in touch.
