Gartner® Report
3 Risks to Avoid in SAP S/4HANA Migrations
SAP ECC End of Life: What Every Migration Leader Needs to Know Before 2027
Overview
SAP ECC end of life is no longer a distant planning concern. With mainstream maintenance ending in 2027, the Gartner® report identifies three risks to avoid in SAP S/4HANA migrations.
Every organization still running SAP ECC is now operating under a hard deadline. The 2027 end of mainstream maintenance is not a warning; it is a forcing function. And yet, as migration programs accelerate to meet it, the decisions made under time pressure are often the ones that shape the S/4HANA environment's stability and performance for years after go-live.
Our 6 Takeaways from Reading the Gartner Report: 3 Risks to Avoid in SAP S/4HANA Migrations
TAKEAWAY 01
SAP ECC end of life is a governance event, not just a technical deadline
Most organizations treat SAP ECC end of life as a system upgrade. As the report states: "In a managed service model, upgrade cycles are less negotiable, meaning code that conflicts with upgrades becomes more disruptive faster."
Every customization carried forward - whether remediating existing code or writing new - must be justified, classified, and documented. Without a formal extensibility governance framework, teams default to ECC-era patterns, creating technical debt that compounds with every upgrade cycle.
TAKEAWAY 02
Your ECC landscape is almost certainly less understood than you think
Every downstream decision in the migration, whether a deployment model, migration path, project scope, phasing or resource estimation, is derived from an understanding of the current ECC landscape. Business process knowledge and technical object knowledge almost never reside with the same people. The mapping between the two - which custom objects support which end-to-end processes and which interfaces feed which downstream systems - is rarely documented coherently. Organizations that proceed without this baseline make scope and cost decisions on assumptions rather than inventory, and systematically underestimate what the SAP ECC end of life transition will actually require.
TAKEAWAY 03
The 2027 deadline creates parallel governance demands most programs are not structured to handle
SAP ECC end of life does not arrive alone. SAP PI/PO, Solution Manager, and GRC 12.0 all reach the end of mainstream maintenance in 2027. These are not sequential problems; they are concurrent ones. Each carries its own migration track, its own governance requirements, and its own extensibility decisions. Organizations running S/4HANA migration programs today are simultaneously managing multiple system-of-record transitions, each of which raises the risk of ungoverned technical decisions made under time pressure.
TAKEAWAY 04
Code that compiles in S/4HANA is not the same as code that is correct
ECC custom code carried forward into S/4HANA can activate without syntax errors and still behave incorrectly. S/4HANA's columnar in-memory database architecture is fundamentally different from ECC's row-based relational model. Fetch logic optimised for ECC forces HANA to work against its design, thereby performing poorly under load and returning incomplete results. This category of failure does not surface in automated scans. It surfaces in production. As the SAP ECC end of life deadline drives migration timelines to compress, the temptation to skip rigorous code assessment grows, and so does the post-go-live cost of getting it wrong.
TAKEAWAY 05
Integration testing scope is almost always narrower than it should be
Testing risk in an S/4HANA migration has two dimensions: depth within the application and breadth across the landscape. Most ECC migration programs achieve one or neither. Processes that span sourcing, warehousing, finance, and third-party systems do not fail in isolation - they fail at the seams between systems. Satellite applications, middleware, and integrations built against ECC-specific data structures inherit risk from every structural change made in S/4HANA. With SAP PI/PO also reaching end of life in 2027, the middleware layer is being rebuilt at the same time as the ERP, thus making landscape-wide test coverage a necessity, not an option.
TAKEAWAY 06
A design authority is the mechanism that keeps the migration clean after go-live
Governance is what makes the difference between a migration that stays clean and one that accumulates a new generation of technical debt. As the report notes: “The risk is not the existence of custom code - it is the absence of a governed decision framework to determine where customization is justified, what form it should take and who is accountable for its long-term maintainability.”
This is distinct from project governance. It is operational governance that persists after go-live, reviewing customization requests, evaluating exceptions, and conducting compliance reviews. For organizations navigating SAP ECC end of life, establishing this framework before migration begins, not after, is the decision that separates programs that stay clean from programs that do not.
TAKEAWAY 01
SAP ECC end of life is a governance event, not just a technical deadline
Most organizations treat SAP ECC end of life as a system upgrade. As the report states: "In a managed service model, upgrade cycles are less negotiable, meaning code that conflicts with upgrades becomes more disruptive faster."
Every customization carried forward - whether remediating existing code or writing new - must be justified, classified, and documented. Without a formal extensibility governance framework, teams default to ECC-era patterns, creating technical debt that compounds with every upgrade cycle.
TAKEAWAY 02
Your ECC landscape is almost certainly less understood than you think
Every downstream decision in the migration, whether a deployment model, migration path, project scope, phasing or resource estimation, is derived from an understanding of the current ECC landscape. Business process knowledge and technical object knowledge almost never reside with the same people. The mapping between the two - which custom objects support which end-to-end processes and which interfaces feed which downstream systems - is rarely documented coherently. Organizations that proceed without this baseline make scope and cost decisions on assumptions rather than inventory, and systematically underestimate what the SAP ECC end of life transition will actually require.
TAKEAWAY 03
The 2027 deadline creates parallel governance demands most programs are not structured to handle
SAP ECC end of life does not arrive alone. SAP PI/PO, Solution Manager, and GRC 12.0 all reach the end of mainstream maintenance in 2027. These are not sequential problems; they are concurrent ones. Each carries its own migration track, its own governance requirements, and its own extensibility decisions. Organizations running S/4HANA migration programs today are simultaneously managing multiple system-of-record transitions, each of which raises the risk of ungoverned technical decisions made under time pressure.
TAKEAWAY 04
Code that compiles in S/4HANA is not the same as code that is correct
ECC custom code carried forward into S/4HANA can activate without syntax errors and still behave incorrectly. S/4HANA's columnar in-memory database architecture is fundamentally different from ECC's row-based relational model. Fetch logic optimised for ECC forces HANA to work against its design, thereby performing poorly under load and returning incomplete results. This category of failure does not surface in automated scans. It surfaces in production. As the SAP ECC end of life deadline drives migration timelines to compress, the temptation to skip rigorous code assessment grows, and so does the post-go-live cost of getting it wrong.
TAKEAWAY 05
Integration testing scope is almost always narrower than it should be
Testing risk in an S/4HANA migration has two dimensions: depth within the application and breadth across the landscape. Most ECC migration programs achieve one or neither. Processes that span sourcing, warehousing, finance, and third-party systems do not fail in isolation - they fail at the seams between systems. Satellite applications, middleware, and integrations built against ECC-specific data structures inherit risk from every structural change made in S/4HANA. With SAP PI/PO also reaching end of life in 2027, the middleware layer is being rebuilt at the same time as the ERP, thus making landscape-wide test coverage a necessity, not an option.
TAKEAWAY 06
A design authority is the mechanism that keeps the migration clean after go-live
Governance is what makes the difference between a migration that stays clean and one that accumulates a new generation of technical debt. As the report notes: “The risk is not the existence of custom code - it is the absence of a governed decision framework to determine where customization is justified, what form it should take and who is accountable for its long-term maintainability.”
This is distinct from project governance. It is operational governance that persists after go-live, reviewing customization requests, evaluating exceptions, and conducting compliance reviews. For organizations navigating SAP ECC end of life, establishing this framework before migration begins, not after, is the decision that separates programs that stay clean from programs that do not.
What the Full Gartner Report Covers
The six observations above frame the challenge. For organizations navigating SAP ECC end of life, the actionable detail sits inside the report itself.
The Gartner report provides specific corrective measures, governance frameworks, and architectural guidance that enterprise application leaders can act on directly.
Make landscape visibility a precondition to strategy selection, not a deliverable of it.
Govern extensibility deliberately through a framework owned by the design authority, with clear decision criteria and architectural oversight, and supported by AI-driven remediation tooling wherever appropriate.
Test at application depth (scenario-based cycles with production-like data) and landscape breadth (end-to-end integration testing across satellite systems and middleware).
Inside the report you will find
What the Full Gartner Report Covers
The six observations above frame the challenge. For organizations navigating SAP ECC end of life, the actionable detail sits inside the report itself. The Gartner report provides specific corrective measures, governance frameworks, and architectural guidance that enterprise application leaders can act on directly.
Make landscape visibility a precondition to strategy selection, not a deliverable of it.
Govern extensibility deliberately through a framework owned by the design authority, with clear decision criteria and architectural oversight, and supported by AI-driven remediation tooling wherever appropriate.
Test at application depth (scenario-based cycles with production-like data) and landscape breadth (end-to-end integration testing across satellite systems and middleware).
“When organizations migrate without full landscape visibility, they systematically underestimate migration cost, scope and operational risk.'
'Without this, the organization either carries forward technical debt it could have retired, or re-creates it within the first year of a new implementation.'
'When testing lacks depth within the application or breadth across the landscape, latent bugs surface in production, disrupting business processes, satellite systems and the go-live itself.”
Gartner, 3 Risks to Avoid in SAP S/4HANA Migrations, 13 May 2026 (G00844976)
Who We Believe Should Read This Report
This Gartner research is written for enterprise application leaders responsible for S/4HANA migration programs. It is particularly relevant for:
CIOs and enterprise architects making deployment model and migration strategy decisions ahead of the SAP ECC end of life deadline
SAP program directors managing brownfield or greenfield conversion timelines under the 2027 constraint
Technical leads and solution architects responsible for ABAP Cloud adoption, extensibility governance, and clean core compliance
IT leaders navigating the concurrent end-of-maintenance deadlines for SAP PI/PO, Solution Manager, and GRC 12.0 alongside the core ECC migration
Unlock the full report and discover the 3 risks to avoid in SAP S/4HANA Migrations and what to do before the 2027 deadline.
Disclaimer: Gartner, 3 Risks to Avoid in SAP S/4HANA Migrations, 13 May 2026, Written for: Enterprise Application Leaders By Ann Paul, Tomas Kienast, Allan Wilkins, Johan Jartelius.
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FAQs Related to Gartner Report - 3 Risks to Avoid in SAP S/4HANA Migrations
SAP ECC end of life refers to the end of mainstream maintenance for SAP ERP Central Component, SAP’s previous-generation ERP platform. SAP has set 2027 as the mainstream maintenance end date, after which standard support – including legal and regulatory updates, quality patches, and performance improvements – will no longer be provided under standard contracts. Organizations still running ECC after this date face increasing support costs, security exposure, and the risk of falling behind on regulatory compliance. Migration to SAP S/4HANA is the primary path forward, but the transition involves significantly more complexity than a standard system upgrade.
Every ECC-to-S/4HANA migration carries risk – but not all risks are equal, and not all programs are structured to catch them before go-live. As the report states: “The three risks described in this research – insufficient landscape visibility, ungoverned extensibility and insufficient testing depth and breadth – are cross-cutting concerns. Each transition raises all three risks to some degree.”
Understanding how these risks interact, where they surface, and what corrective measures to put in place is what the full report covers. Download it to get the complete picture.
SAP ECC mainstream maintenance ends in 2027, which means organizations are now in the final phase of viable migration planning. Enterprise S/4HANA migration programs typically require 18 to 36 months from program initiation to go-live, depending on landscape complexity, migration strategy, and the scope of integration replatforming required. Organizations that have not yet completed a landscape assessment and selected a migration strategy are at risk of arriving at the 2027 deadline without a stable, tested S/4HANA system in place.
As the report states: “Architectural decisions made during this period, and equally the ones deferred, compound after go-live and shape the S/4HANA environment’s maintainability, upgrade path and innovation readiness for years.”
A brownfield migration converts the existing ECC system to S/4HANA, carrying forward the current configuration, data, and custom code. It is typically faster but inherits the full weight of the existing ECC landscape – including processes, data, and objects that may no longer serve a current business need. A greenfield reimplementation builds a new S/4HANA system from scratch using SAP standard as the baseline. It offers more opportunity to adopt clean core principles from the start but requires a thorough understanding of the existing ECC landscape to determine what the new system needs to replicate, what can be retired, and where gaps may emerge. A third option – selective data transition – migrates specific data objects and processes rather than the full system, concentrating risk in the scoping decisions themselves.
SAP Process Integration and Process Orchestration (PI/PO) reaches end of mainstream maintenance in 2027, at the same time as SAP ECC end of life. Organizations must replatform to SAP Integration Suite or a third-party iPaaS – but this is not a lift-and-shift exercise. Custom adapters, user-defined functions, and complex message orchestration must be identified, redesigned, and rebuilt. The risk is treating replatforming as a technical migration when it is effectively a rearchitecture. For ECC migration programs, this creates a dual deadline: the ERP migration and the middleware migration must be sequenced, tested, and governed in parallel, each with its own landscape dependencies and test scope requirements.
A landscape assessment is the process of mapping an organization’s current ECC environment to produce a clear inventory of what the system actually contains – which custom objects exist, which end-to-end processes they support, which integrations feed which downstream systems, and where technical debt has accumulated.
As the report states: “Every downstream decision in the migration – deployment model, migration path, project scope, phasing, fit-to-standard evaluation, integration planning, resource estimation – is derived from an understanding of the current landscape. If that understanding is incomplete, fragmented across teams or simply undocumented, those decisions are educated guesses and not representative of the full facts.”
The full approach recommended in the report, including the artifacts this mapping produces and how to sequence it against your migration strategy selection, is detailed inside.
Effective S/4HANA migration testing requires two dimensions that most ECC migration programs fail to achieve simultaneously. Depth means scenario-based testing cycles using production-volume data against actual business processes – not just automated compliance scans. This catches failures specific to S/4HANA’s data model that only surface under realistic conditions, such as field length changes or incomplete results from direct table reads in a Business Partner-enabled system. Breadth means end-to-end integration testing across the full landscape – including satellite applications, middleware, and third-party systems – not just the S/4HANA core. With SAP PI/PO also reaching end of life in 2027, breadth testing must cover the rebuilt middleware layer as well as the ERP itself.