Order is the soul of everything

Why is it worth getting things in order in SAP BW before the migration?

Introduction: the decision point

The future of existing SAP BW data warehouses is a pressing issue for many domestic companies: support for older systems, such as BW on HANA, will expire on December 31, 2027. After that, the system can typically continue to be operated under an Extended Maintenance arrangement, which extends the deadline to 2030 at the cost of additional operating expenses.

There are several ways to address this situation, such as:

Migrating to SAP BW/4HANA,
Migrating to Business Data Cloud.

Whichever path we choose, the cost of the migration typically consists of two components:

Licensing and infrastructure costs (which are heavily influenced by sizing),
project costs (migration, development, testing, business engagement).

The good news is that there is one step that, in most cases, reduces both the cost of the transition and the project risk. This is well-planned and thoroughly executed BW housekeeping.

What is BW housekeeping, and why is it relevant right now?

BW housekeeping is not an end in itself, but rather a deliberate effort to reduce scope and size prior to the migration, with a goal that can be simply stated as follows:

do not migrate or test anything that is no longer in use,
do not pay for licenses to store unnecessary data,
do not carry over obsolete system components to the new platform.

In practice, this manifests itself in three very tangible ways.

1) Filtering out unused objects: smaller scope, less testing

Over the years, most data warehouses accumulate developments, reports, data streams, and objects that:

no longer support active business processes,
have been replaced by another solution,
or have simply been “forgotten”.

During BW housekeeping, a list of objects can be compiled based on data load logs and execution statistics, for which it can realistically be stated that migration is not necessary.

What are the benefits?

Shorter and less expensive migration/development phase,
less chance of error,
significantly reduced testing requirements on both the supplier and customer sides.

Experience shows that the savings here are not only financial, but also result in reduced project risks, lower resource requirements for the project, and, in the long term, increased operational efficiency.

2) Reducing storage requirements: a direct impact on licensing costs

For data warehouses, licensing costs are largely determined by the amount of storage required. It is not uncommon for a BW system to contain 15–20 years’ worth of data, even though significantly less data is typically sufficient for day-to-day business operations.

One of the key steps in housekeeping is therefore:

business consultation on how many years of data are actually required in the various business areas,
considering legal compliance requirements,
and finally selective deletion, data reduction.

It is important to note that over the years, it is not only the volume of business-related data that grows in data warehouses; in many cases, technical data can also take up a significant amount of space, such as:

PSAs,
IDocs,
various logs,
technical tables and historical auxiliary data (e.g., accumulation of exchange rate tables).

These often grow “silently” in the background to sizes in the hundreds of gigabytes, consuming storage space and driving up migration costs while creating little to no business value.

3) More accurate sizing leads to better decisions during the migration

As long as the system is full of “legacy” data and objects, sizing tools (and, consequently, the licensing and infrastructure plan) are likely to overestimate.

If housekeeping is thorough and comprehensive, then:

it is possible to more accurately determine the required size of the data warehouse,
when considering the SAP ecosystem, sizing tools also yield more realistic results,
and the migration strategy (BW/4HANA vs. other approaches) is based on clearer figures.

Important: housekeeping is not exclusively a vendor or IT task, nor is it merely “technical cleanup.” Making good decisions requires the active involvement of the client’s key users and BW experts, as they are the ones who can reliably determine what is in use, which data is critical, and what can be safely deleted from the system. This work cannot be skipped; failing to do so significantly increases the project’s risk!

Case study: a profitable investment, streamlined for the new year

The following is a brief summary of the results of our housekeeping project conducted at the end of 2025 for a client operating in the energy sector.

What did we examine?

In the existing BW environment, we analyzed the usage and storage requirements for each object type.

The most important findings:

here were data sources in the system linked to temporary storage areas (PSAs) that were not included in the regular deletion chain,
The system contained 21 years’ worth of data, even though 8 years is generally sufficient for the client,
IDocs, logs, and exchange rate tables were not properly maintained.

What did we do?

By purging the PSAs, we managed to reduce the system size from 700 GB to 590 GB.
We then used selective deletion to remove data older than 8 years and performed maintenance on the technical tables as well.

Result: The system size shrank to 480 GB, representing a reduction of more than 30% compared to the initial state. This alone means that the data warehouse’s licensing costs have decreased proportionally—and, in addition, the migration scope and testing workload have also been reduced.

(Note: The exact amount of savings always depends on the system’s composition, retention policies, and business requirements.)

When is the right time to get started?

If the transition is realistically on the agenda within 1–2 years, then housekeeping is the step that:

can be launched with low risk,
delivers measurable results quickly,
is a useful activity regardless of the platform.

In practice: the sooner you get organized, the cheaper and cleaner the system modernization will be.

Housekeeping is not extra work, but a rational decision

Migration projects to BW/4HANA (or other systems) often seem daunting due to licensing and project costs. BW housekeeping, however, significantly helps streamline these costs by:

it reduces the scope of migration,
it alleviates the testing burden,
and generally has a direct impact on licensing costs as well.

In Onespire’s experience, BW housekeeping substantially reduces the cost and risk of migration. If you’d like to assess quick savings opportunities in your BW environment, our team of experts would be happy to help—we look forward to hearing from you.