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Introduction

Hello everyone and welcome back to my blog. Today we’re diving into one of the most important decisions an organisation will ever make in their SAP journey – how to actually implement S/4HANA.

Now, if you’ve been following along with my videos or blogs, you know that the mainstream support for SAP ECC support is ending in 2027 and the extended support is available until 2030. This means hundreds of thousands of companies worldwide need to make the jump to S/4HANA in the next few years. But here’s the thing – there isn’t just one way to do this migration. In fact, there are three main approaches, and choosing the wrong one could cost you millions of dollars and years of headaches.

Think of it like renovating your house. You could tear everything down and build from scratch, you could work with what you’ve got and just upgrade the essentials, or you could take a hybrid approach – keeping the good stuff and replacing what’s not working. That’s exactly what we’re dealing with here, but instead of kitchens and bathrooms, we’re talking about your entire business system.

The Three Main Approaches

Let me break down the three main approaches for you: Greenfield (which is your fresh start), Brownfield (your upgrade approach), and Bluefield (your best-of-both-worlds hybrid).

Greenfield Approach – The Fresh Start

First up, let’s talk about Greenfield implementation – and it’s called that because you’re literally starting on a green, empty field.

What is Greenfield?

With Greenfield, you’re implementing SAP S/4HANA as a completely new system from scratch. You’re not carrying over any of your unwanted data, configurations, or customizations. It’s like buying a brand new house instead of renovating your current one.

Here’s how it works: Your project team builds a brand new S/4HANA environment, configures it according to SAP best practices, and then migrates only the essential data from your old system. Everything else gets left behind.

Real-World Example

Let me give you a real world example. I once worked with a manufacturing company that had been using SAP for over 15 years. Their system was like a house that had been renovated by 10 different owners – patches everywhere, custom code that nobody understood anymore, and processes that made absolutely no sense. They chose Greenfield because they wanted a clean slate.

The result? They went from having over 2000 custom programs down to just 200. Their month-end close went from 10 days to 3 days. But here’s the kicker – it took them more than 2 years to complete, and they had to retrain their entire workforce.

When Should You Choose Greenfield?

Greenfield is perfect if your current SAP system is heavily customized, inefficient, or if you want to completely redesign your business processes. It’s also great if you’re looking to standardize across multiple locations or if you’re planning significant organizational changes.

The Pros and Cons

On the plus side, you get the cleanest possible S/4HANA implementation. You’re using SAP best practices, you get all the latest features, and you won’t carry forward any technical debt. Plus, you can take advantage of cloud deployment options more easily.

The downside? Time and cost. We’re talking 24 months or more typically. You’ll also lose all your historical transactional data unless you specifically plan to migrate it, which adds complexity and cost.

Brownfield Approach – The System Conversion

Now let’s talk about Brownfield, which is essentially upgrading your existing system to S/4HANA.

What is Brownfield?

With Brownfield, you’re converting your existing SAP ECC system directly to S/4HANA. Think of it like renovating your current house – you keep the foundation, the basic structure, and most of your belongings, but you upgrade the essentials.

Technically, this involves a database migration to SAP HANA, converting your data from the ECC data model to the S/4HANA data model, and upgrading your application code. All your historical data, customizations, and configurations come along for the ride.

But here’s where it gets really interesting – and this is something most people don’t talk about enough. A Brownfield conversion isn’t just a simple upgrade. You need to go through several critical preparation steps that can make or break your project.

Let’s take a look at The Critical Preparation Steps

Before you even think about hitting that conversion button, you need to complete what I call the “Big Four” preparation activities:

1. SAP Readiness Check

This is your system health assessment. The SAP Readiness Check is a free tool that analyzes your current ECC system and tells you exactly what needs to be fixed before conversion. It’s like getting a building inspection before renovation.

The tool examines everything – your installed components, custom code, data volumes, hardware requirements, and business processes. It then generates a comprehensive report showing you the green lights, yellow warnings, and red stop signs.

Running the readiness check is a very important step that should never be skipped. I’ve seen companies try to shortcut this step and end up with conversion failures that cost them months of rework. The tool is free, takes about a day to run, and could save you millions.

2. Simplification Item Check

SAP S/4HANA has simplified many processes compared to ECC, but that means some of your existing configurations might not work anymore.

The Simplification Item Check identifies all the functionalities in your system that will be affected by these simplifications. For example, if you’re using old-style profit center accounting, the check will tell you that you need to switch to the new Universal Journal approach.

Think of it like this: if you’re renovating your house and want to install new smart appliances, you need to check if your electrical system can handle them. The Simplification Item Check does exactly that for your SAP system.

You run this check using the report /SDF/RC_START_CHECK, but you need to implement SAP Note 2502552 first. SAP provides detailed notes on how to run this check.

3. Custom Code Remediation

Here’s the big one that keeps ABAPers awake at night. Your custom ABAP code that works perfectly in ECC might completely break in S/4HANA.

Why? Because S/4HANA uses the HANA database, which has different SQL syntax requirements. Plus, SAP has changed many standard tables and function modules. Your custom reports that reference table BSEG for example won’t work because in S/4HANA, that data is now in ACDOCA (the Universal Journal table).

The good news is that modern tools can automatically remediate 70-80% of these issues. I’ve seen companies with 10,000+ custom programs get through remediation in just a few months using automated tools, compared to the 2-3 years it would take manually.

My advice is that Start your custom code analysis early. Use tools like the Custom Code Migration app or third-party solutions. Don’t try to do this manually unless you enjoy pain.

4. Business Process Adjustments

This is the part that really impacts your end users. S/4HANA doesn’t just change the technology – it changes how you do business.

The biggest change is that the Customer and Vendor Master Data becomes Business Partners. In ECC, customers and vendors were separate objects. In S/4HANA, they’re unified under the Business Partner concept.

Let me give you a real example. In ECC, if Company ABC was both your customer and vendor, you’d maintain two separate master records. In S/4HANA, Company ABC becomes one Business Partner with multiple roles – customer role and vendor role.

This isn’t just a technical change. It affects your data entry processes, your reporting, and even your organizational structure. You need to set up Customer-Vendor Integration (CVI) before your conversion. This process can take weeks or even months, depending on your data quality and complexity.

Let me give you a Real-World Example

I recently learnt about a retail company’s Brownfield conversion approach. They had a solid ECC system with good processes but needed the performance benefits of HANA database. The conversion took them 18 months, and they were able to keep 95% of their existing configurations and customizations.

But here’s what they did right: They spent a good amount of time on preparation that included Readiness Check, Simplification Item analysis, custom code remediation, Data Archiving and Business Partner conversion and testing.

The beauty was that their users barely noticed the difference. Same screens since they were already using Fiori, mostly the same processes, just faster performance and some new capabilities. Their inventory processing that used to take overnight batch runs now happens in real-time.

When Should You Choose Brownfield?

Brownfield is ideal if you’re happy with your current business processes and your ECC system is relatively clean. It’s also great if you need to minimize disruption to your business operations or if you have limited time and budget.

You should definitely consider Brownfield if your users are comfortable with the current system and you don’t want to invest heavily in change management and training.

The Pros and Cons

The biggest advantage is speed and cost. Most Brownfield conversions take 12-18 months and it could be less for smaller organisation. Which is significantly less than the Greenfield appraoch. You keep all your historical data, customizations, and user familiarity.

The downside? You’re carrying forward all your technical debt. Those custom programs that were causing issues in ECC? They’re coming with you. You also might not get the full benefit of S/4HANA’s simplified data model if you’re not willing to adapt your processes.

Understanding the Data Model Changes

Let me quickly explain the major data model changes you’ll encounter in Finance for example.

Universal Journal (ACDOCA)

In ECC, your financial data was spread across multiple tables – BKPF/BSEG for Financial Accounting, COEP/COSP for Controlling. In S/4HANA, all this data goes into one table called ACDOCA, the Universal Journal. This gives you real-time integration between FI and CO, but it means all your financial reports need to be adapted.

Account-Based CO-PA

If you’re using Costing-based Profitability Analysis in ECC, you’ll need to switch to Account-based CO-PA in S/4HANA. This provides better integration with the General Ledger but requires process changes and training.

New Asset Accounting

The old Asset Accounting is gone. S/4HANA uses New Asset Accounting, which is fully integrated with the Universal Journal. This affects your depreciation runs, reporting, and month-end processes.

I have made another video explaining the differences between SAP ECC and S/4HANA in my YouTube channel.

Bluefield Approach – The Best of Both Worlds

Finally, let’s discuss Bluefield – the hybrid approach that’s becoming increasingly popular.

What is Bluefield?

Bluefield, also called Selective Data Transformation, gives you the flexibility to selectively choose what to keep and what to redesign. You create a new S/4HANA system but then selectively migrate data, configurations, and customizations based on their business value.

Think of it like renovating your house room by room. You might completely redesign the kitchen because it’s outdated, keep the living room because it’s perfect, and partially update the bedrooms.

How It Works

With Bluefield, you typically start with what’s called a “shell conversion” – you create a copy of your production system without the master or transactional data, convert it to S/4HANA, and then selectively migrate back the data and configurations you want to keep.

The magic happens in the selection process. You can choose to migrate financial data from the last 2 years but leave behind older transactions. You can bring over master data but redesign your organizational structure. You can keep certain customizations but replace others with standard S/4HANA functionality.

Real-World Example

Let’s talk about a real world example. Let’s say a Global company that had operations across 25 countries. They used Bluefield to consolidate from 5 regional ECC systems into a single global S/4HANA system. They selectively migrated active customers and suppliers but left behind inactive ones. They kept their successful sales processes but redesigned their procurement processes.

The result was a 40% reduction in system complexity while maintaining business continuity. The project took 18 months, which was longer than Brownfield but shorter than a full Greenfield implementation.

When Should You Choose Bluefield?

Bluefield is perfect if you want to optimize your processes but can’t afford a complete redesign. It’s also ideal for system consolidations, phased rollouts, or when you want to minimize downtime.

Consider Bluefield if you have a mix of good and bad processes, if you’re dealing with data quality issues, or if you want to take a country-by-country or business-unit-by-business-unit approach.

The Pros and Cons

The advantage is flexibility. You get to keep what works and fix what doesn’t. You can also handle complex scenarios like system consolidations or organizational restructuring.

The challenge is complexity. Bluefield requires significant expertise and planning. You need to carefully analyze every piece of data and every process to decide what to keep, what to modify, and what to replace.

Making the Right Choice

So how do you choose between these approaches? Let me give you a framework that a lot of customers use to choose their approach.

Consider Greenfield if:

• Your current system is heavily customized with poor performance
• You want to standardize processes across multiple locations
• You’re planning significant organizational changes
• You have the time and budget for a complete transformation
• Your users are open to learning new ways of working

Consider Brownfield if:

• Your current ECC system is relatively clean and well-maintained
• You’re satisfied with your existing business processes
• You need to minimize disruption and costs
• Your users prefer minimal change
• You have tight timelines (remember, ECC support ends in 2027)
• You’ve successfully completed Readiness Check and Simplification Item analysis

Consider Bluefield if:

• You want to optimize some processes but not others
• You’re consolidating multiple systems
• You have data quality issues that need addressing
• You want a phased approach to change
• You have the expertise to handle selective migration

Critical Success Factors

Regardless of which approach you choose, here are the critical success factors that you must follow to ensure a successful S/4HANA conversion program.

1. Executive Sponsorship

This cannot be a purely IT project. You need business leadership driving the change.

2. Data Quality

Poor data quality will kill any migration approach. Start cleaning your data early. This is especially critical for Business Partner conversion in Brownfield projects.

3. Change Management

Even with Brownfield, users need support and training. Don’t underestimate the impact of process changes like Business Partner integration.

4. Testing Strategy

Plan for multiple rounds of testing. I recommend at least 30% of your project timeline should be dedicated to testing. For Brownfield, test your conversion process multiple times in sandbox environments.

5. Cutover Planning

Have a detailed cutover plan with multiple rehearsals, especially for Brownfield conversions. Practice your conversion procedure in development and test systems before attempting production.

Common Pitfalls to Avoid

Let me share some mistakes I see companies making repeatedly:

Don’t just “lift and shift” – Even with Brownfield, take the opportunity to clean up your system. Use the mandatory Business Partner conversion as a chance to clean up your master data.

Don’t underestimate custom code – That ABAP code you wrote 10 years ago might not work in S/4HANA. Start your custom code analysis early and budget for proper remediation. Make use of automated tools and consider clean core concepts.

Don’t ignore the 2027 deadline – With average project timelines of 12-18 months plus preparation time, you need to start planning now.

Don’t forget about integration – Your S/4HANA system doesn’t exist in isolation. Plan for all your interfaces. Many PI/PO interfaces will need to be redesigned.

Don’t skip the Readiness Check – I cannot stress this enough. The SAP Readiness Check and simplification item reports are free and could save you from major conversion failures.

Don’t underestimate the Business Partner conversion – This isn’t just a technical exercise. It affects your business processes, reporting, and user training.

That’s all for today’s deep dive into S/4HANA implementation approaches. If this helped clarify things for you, like the video and subscribe for more ERP content that actually makes sense.