Well, there are more number of on-line resources about Master Data in SAP IS-U, thanks to those authors.
SC Blogs:
SAP IS-U data model - Business and Technical Master Data
SAP wikis:
How to Create Technical Master Data - Utilities Industry - SCN Wiki
But, what happens when you decide to change your basic Data Model in your IS-U? wait, why do you want to do this? To give you a scenario, in one of my previous project the data model was not standard in first place, and we have to change this to standard best practise, and now you got why this blog!
By not standard I mean, initially, for each divisions i.e. for Electricity service and for Gas service, users were using individual Contract Accounts and also individual technical master data. This means duplicate of data and business processes. Now in this case we have to change the data model towards as standard SAP IS-U approach as possible with minimum impact to the current business process.
There could be many ways to change this Data Model, but I am not going into detail of each, as it depends on specific client/project situation/scale/time/money...etc, few methods are below:
A) Having a custom migration process (initially thought of one-off process) where we did updates to the master data tables.
B) For affected scenario, perform Move-out of one fuel and perform move-in (no need of much custom developments compared to A).
Each method will have its own pros and cons, needs further custom enhancements and logic to be implemented at various process within IS-U.
Note: I will update this blog regularly and add my knowledge gained during the support of this project after go-live.