SAP provides various options to migrate from legacy BW systems to BW/4 HANA:
- In Place: Convert the existing BW system to BW/4 HANA
- Remote: Install new system and selectively migrate BW Objects and Data (no selection option available for Data migration)
- Shell Conversion: Install new System and selectively migrate BW Objects. Conversion tool does not provide any options to migrate data; we will have to use standard BW techniques to load data.
Shell approach gives flexibility in changeover and helps fulfil the customer needs in a significant way with the salient features as mentioned below.
- Supports the carve out scenarios more efficiently since there is no Requests association. This is unlikely with Remote or IN-place conversions
- High flexibility for the customers in making decisions on the data retention policy of the legacy Data.
- Advantage for the customer to build a clean BW/4HANA system with the option to cherry pick and carry forward their existing data flows with relevant data sets or even start fresh with the option to leave the legacy data behind. (Accelerated green field )
- Flexibility to optimize the existing flows and incorporate the BW contents at the same time
Know more about shell conversion through BW/4HANA Webinar Series
In this blog we will be focusing on how to handle historical data loads during a BW/4 HANA migration using Shell Conversion. The 2 options available for loading legacy data are:
- Load data from Source systems
- Load data from legacy BW system
Loading from original source system has the following disadvantages:
- Not all the data will be available in the sources (retired legacy systems, data archived etc.)
- Loading from original source does not allow loading data directly to the final targets in BW/4 and will have to go through the data flows requiring further troubleshooting.
Recommended approach: Load data from Legacy BW to BW/4 Data target using a 1:1 mapping
Legacy Data + Delta Management in Shell Conversion
The above pic illustrates the high level dataflow into and within the BW/4HANA System from Original BW as well as from the Original source connected.
When we talk about the Historical data load using the ODP data sources from the Original BW and the relevant quiet time in original BW during the historical load; we can achieve this with a proper cutover plan.
Arrangements for Making B4H System for Historical Load
Source System & Data Sources
As an initial task to prepare the B4H box ready for the historical load we have to create a source system for the Original BW system in BW/4HANA.
The Source system should be created as a Myself BW System (ODP_BW) in B4H which enables the developer to replicate the data sources corresponding to each info provider from the Original BW system and this can be used for further feeding historical data in B4HANA system.
Ref.SAP Note : https://launchpad.support.sap.com/#/notes/2481315
Transformation & DTPs
We can create the DTP with relevant restrictions as per the data requirements and can trigger a full load either specific to the Info provider or through the process chains designed for historical data load.
The flow will be something similar as in the below pic once we created the Transformations & DTPs
High Level Cutover Plan & Requirements
- Make Sure all the Objects involved in the flow are Active in both the System ( Old /New BW )
- Make sure all the delta records that have already been received from the source are uploaded in Original BW targets completely.
- Both Original & New BW System should connected to same source to resume the Delta load later.
- Stop all the process chains scheduled in the original BW and make sure no more data load to the Original BW until the release of quiet time.
Originally published at https://www.applexus.com.