Legacy system decommissioning: How to evaluate the right approach

Author: Priyasha Purkayastha, Global Content Manager, TJC Group

With SAP ECC’s end of mainstream maintenance fast approaching, organisations face a critical decision: what to do with their legacy SAP systems. It is imperative that you understand and evaluate the right decommissioning approach. System retirement is a tedious process and ensuring a smooth, cost-effective transition is of utmost importance. This guide walks you through every major point for evaluation, the common pitfalls to avoid, and the best approach you can opt for. Read on to know more!

Introduction

The deadline to ending mainstream maintenance for SAP ECC is fast-approaching. The question of how to handle these legacy systems has moved from the back burner to the boardroom, where simply ignoring the problem is no longer viable. The costs of maintaining outdated systems, the cybersecurity risks they pose, and the compliance gaps they create all demand action.

However, not all legacy system decommissioning approaches are created equal. The right strategy depends on your organisation’s size, regulatory landscape, data volumes, IT infrastructure, budget, and long-term digital transformation goals. To ensure the right approach to legacy system decommissioning, there are several factors that organisations must consider. In this blog, we discuss not only how to evaluate the right approach, but also why it matters and more.

What is legacy system decommissioning?

To start with, let’s talk in brief about how decommissioning of legacy systems works. Simply put, it can be touted as the planned, structured process of permanently retiring an obsolete IT system, whether SAP or non-SAP, while preserving the historical data it contains for future access. On contrary to the common misconception, it is not simply switching off a server; rather, it involves extracting data, documents, and reports from the legacy system, storing them securely, and ensuring they remain accessible for compliance, audit, and business purposes.

A properly executed decommissioning project achieves three core objectives:

Data preservation: Historical data is extracted and stored as a tax archive, with proof of completeness and non-modification, ensuring it meets legal and regulatory requirements.

Cost elimination: Licensing fees, infrastructure costs, maintenance overheads, and resource expenses associated with the legacy system are removed.

Risk reduction: Security vulnerabilities, compliance gaps, and technical debt associated with running outdated software are eliminated.

It is important to distinguish legacy system decommissioning from data migration. Migration moves a subset of data into a new system for operational use, whereas decommissioning focuses on retiring the entire legacy environment while preserving access to its complete historical dataset. The two are complementary but should ideally be managed as separate projects.

Why choosing the right approach matters

Selecting the wrong SAP decommissioning approach can have far-reaching consequences. Here is why the decision deserves careful consideration:

Financial impact

According to reports, approximately 70% of IT budgets are spent on maintaining legacy systems. Each legacy system carries up to 49 different cost implications, from software licensing and database fees to infrastructure and specialist personnel. The right decommissioning approach can save organisations hundreds of thousands of pounds annually.

Compliance and legal exposure

Tax authorities in most jurisdictions require organisations to retain financial records for seven to ten years, and HR data for even longer in some countries. A decommissioning approach that fails to provide proof of data completeness and non-modification will not satisfy auditors. Choosing an approach that does not support data privacy requirements, such as GDPR-compliant data deletion, exposes your organisation to significant fines.

Security risks

Legacy systems that are no longer patched or updated are prime targets for cyberattacks. Several cybersecurity reports highlighted that keeping up with patches remains one of the most significant challenges for IT security teams. An approach that leaves legacy data in an unpatched, vulnerable environment is not a viable long-term solution.

Operational efficiency

The right approach frees up IT resources, simplifies your system landscape, and allows your teams to focus on strategic initiatives rather than maintaining obsolete technology. Conversely, a poorly chosen approach can create ongoing maintenance burdens and technical debt.

How to evaluate the right approach for your organisation

Choosing the right SAP decommissioning approach requires a structured evaluation against several key criteria. The following framework can help guide your decision:

Compliance requirements

Start by mapping your regulatory obligations. Which jurisdictions do you operate in? What are the data retention periods for financial, HR, and operational data? Do you need to comply with GDPR, CCPA, DPDP (India), or other data privacy laws? Your chosen approach must support both long-term data retention and the ability to delete personal data on request.

Total cost of ownership

Look beyond the upfront project cost and calculate the total cost of ownership over five to ten years. Factor in licensing fees, infrastructure costs, maintenance, specialist personnel, and the opportunity cost of IT resources tied up in legacy system management. Remember that the hidden costs of maintaining legacy systems often exceed the visible ones.

Data volume and complexity

Assess the volume of data in your legacy systems and the complexity of your data model, including custom tables and fields. Large, complex environments with tens of terabytes of data require approaches that can handle extraction at scale without compromising data integrity.

Security posture

Evaluate the security implications of each approach. Does it eliminate the legacy system entirely, or does it leave a vulnerable footprint? Does it provide encryption, role-based access controls, and audit logging? In an era of rising cyber threats, security should be a non-negotiable criterion.

User accessibility

Consider who will need to access the legacy data and how frequently. Tax and audit teams, compliance officers, and business users all have different needs. The chosen approach must provide intuitive, easy-to-use access, particularly for users who may never have worked with the original legacy system.

Future scalability

Think beyond the immediate decommissioning need. Will the approach support future AI and analytics initiatives? Can it accommodate additional legacy systems as your organisation continues to evolve? A forward-looking approach turns legacy system decommissioning from a cost centre into a strategic enabler.

TJC Group’s Enterprise Legacy System Application (ELSA)

TJC Group’s Enterprise Legacy System Application (ELSA), built on SAP Business Technology Platform (BTP), is one of the leading approaches for both non-SAP and SAP decommissioning.

How it works: ELSA follows a structured four-step process

Full data extraction: 100% of accessible data is extracted from the legacy system and saved as tax archives in AIS format (SAP’s audit format), which is compact, metadata-rich, and provides proof of completeness and non-modification

Secure cloud storage: Extracted files are stored in the customer’s preferred cloud environment (AWS, Azure, GCS, OVHCloud) or on-premises file systems

Selective database import: Business-critical data is imported from the flat files into a database of choice (SAP HANA, Oracle Heatwave, MySQL, or PostgreSQL) for fast retrieval

User-friendly access: Authorised users access historical data through ELSA’s FIORI-style UI5 interface, with pre-configured transactions, static reports, dynamic reporting, and GenAI-powered text-to-SQL queries

Advantages of TJC Group’s ELSA

• Supports both SAP and non-SAP decommissioning through a single, unified platform
• Tax archive compliance: AIS format provides proof of completeness, non-modification, and full traceability, meeting the strictest audit requirements
• Data privacy by design: ELSA’s patented approach allows it to function simultaneously as a tax archive and a data privacy-compliant solution, supporting surgical data deletion without compromising archive integrity
• Low infrastructure overhead: No additional SAP systems required; runs on SAP BTP Cloud Foundry
• Flexible deployment: Works with any major hyperscaler, smaller cloud providers, or on-premises storage
• Cost-effective: Eliminates all legacy system licensing, infrastructure, and maintenance costs.
• Future-proof: Historical data can be connected to analytics pipelines and AI solutions, turning legacy data from a burden into a strategic asset
• ISO 27001 certified: TJC Group follows the latest security best practices, with daily vulnerability checks and regular third-party penetration testing

Common pitfalls to avoid when choosing decommissioning approach

Even well-intentioned SAP decommissioning projects can go wrong. Here are the most common pitfalls and how to avoid them:

Pitfall 1: Treating decommissioning as an afterthought

Many organisations focus entirely on the S/4HANA migration and leave decommissioning as a last-minute concern. This leads to rushed decisions, inadequate planning, and suboptimal outcomes. Make decommissioning a core part of your IT strategy from the outset.

Pitfall 2: Relying on ETL/ELT tools for tax archiving

Database-to-database transfer solutions based on ETL (Extract, Transform, Load) or ELT (Extract, Load, Transform) approaches may not provide proof of non-modification and often cannot guarantee data completeness. These tools are designed for data integration, not for creating compliant tax archives.

Pitfall 3: Underestimating data privacy requirements

Legacy systems were not designed for modern data privacy laws. Simply extracting data and storing it in a new location does not automatically make it GDPR-compliant. Your decommissioning solution must support data deletion and anonymisation requests while maintaining tax archive integrity.

Pitfall 4: Ignoring the total cost picture

Focusing solely on the upfront project cost while ignoring the ongoing costs of the chosen approach is a recipe for budget overruns. A VM that appears cheap initially can become extremely expensive when factoring in security patching, boot-up time, and eventual obsolescence.

Pitfall 5: Combining migration and decommissioning

Attempting to handle migration and decommissioning within the same project creates complexity on both sides. Migrated data does not serve as a valid historical archive, and trying to split data between the new system and a decommissioning solution leads to incomplete datasets in both.

Conclusion

Keeping legacy systems running or freezing them in virtual machines may appear attractive in the short term but carry unsustainable long-term risks. Cloud-based legacy system applications like ELSA offer the most comprehensive, flexible, and future-proof solution for legacy system decommissioning.

Ready to take the next step? Contact TJC Group today and discover how we can help you choose and implement the right decommissioning approach for your SAP landscape!

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