Hi,
SAP Data migration is combination of technical and functional streams.
Workflow will be like this,
Once requirements gathered and process and solution defined in ECC and basic configuration is defined. Functional team need to list all the Data requirements in terms of specifications with all SAP requirements
These specifications need to be validated by Business and BPO's and then shared with DM work stream where DM Business analysts start studying the Legacy and map to the SAP requirements.
Once the mapping part done, Technical team (ETL) will implement this through ETL tools or any other way to get final data in terms of SAP Requirements and fit for SAP.
This can be loaded in to SAP through ETL tools directly or through LSMW.
There will be validations done at various levels by Business and Functional leads to make sure the final data is in terms of requirements and fit for purpose.
any changes in solution leads to Spec changes and followed by mapping changes which will be part of Program Change process.
Thumb Rule:
SAP is a process-oriented System and master data is an integral part of this Process.
This means that everything is integrated together and tightly coupled to the system configuration. Master data is dependent on the configuration, the configuration is designed to support your processes, and master data is needed to run your process.
Thanks,
Srinivas