Strategies for migrating from SAP BW to HANA

There are many ways to move an existing SAP BW system on a traditional database to SAP BW on HANA, but there are really only two major strategies which most companies consider: New implementation (greenfield) and database migration.Within each strategy, there are different approaches and tactics which can be employed. Let’s dive a little deeper into the benefits, approaches, and tactics of both strategies.

New implementation (greenfield) strategy
In a new implementation, or greenfield strategy, a conscious decision has been made to install an entirely new SAP BW on HANA environment. Content (i.e., data models, applications, and reports) from the original SAP BW system will be redeveloped in the SAP BW on HANA system. This greenfield system will run in parallel with the existing BW environment for the duration of time it takes to redesign the entire enterprise data warehouse (EDW) to fully leverage the benefits of the SAP HANA platform.

When the new system is ready, historical data can be migrated from the old environment to the greenfield system. As reporting capabilities are rolled out, one or more production cutovers can be scheduled to transition the business to the new system, thus enabling a flexible deployment approach.

The biggest deterrent to the greenfield approach is the cost of implementation and the lost investment in the original system. Depending on the size and complexity of the original SAP BW system, a greenfield approach could take multiple years to completely redesign and rebuild, thus requiring a dual landscape (twice the infrastructure and twice the support) during that time. For systems with severe design issues or minimal content, the effort of rebuilding from scratch may be well worth it considering the benefits of this strategy.

The biggest benefit of the greenfield strategy is that it provides an opportunity to completely discard and/or replace old, outdated, and overly complex data models. In many cases, data models and data flows designed for reporting efficiency in traditional SAP BW implementations can be simplified in SAP HANA. In other cases, flawed data models or data flows can be discarded and replaced with a better design.

This strategy also allows for a less stressful migration, since the old system remains operational with no disruptions while the new system is being implemented. In our experience, the greenfield approach has been used in approximately one third of SAP BW on HANA implementations.

Database migration strategy
In most cases, a significant investment has been made in the original system. The data flows align with a layered scalable architecture (LSA) and the data models adhere to best practice modeling guidelines. The queries and reports based on the original system deliver the right results. Many years of requirements gathering, design, development, and testing effort have been spent building the system, and there is no reason to discard or replace what has already been built.
The best strategy for these types of systems is to migrate the database from the original database to SAP HANA. Depending on the size of the system, there are two basic approaches which can be followed: In-place migration and downtime-minimized migration.

For smaller databases, usually less than 10 TB, the in-place migration is the simplest, most efficient, and most economical approach.

Keep reading in the SAP BW HANA Migration Handbook by Rob Frye, Joe Darlak, and Dr. Bjarne Berg.