BI Content in SAP BW

Hello Experts,

I have a Question.

Whenever, we do replication of datasources from Source system to BW , the version(3x or 7x) is determined considering in which version the datasource is available in BI content right.

So, how is that determined ? That in which version a specific datasource should reside in.

We have a Suituation in which , we have two source systems A & B.

A contains certains datasources in 3x version, but in B those are in 7x (Even in BI content).

B is a copy system of A. Only difference is B is a upgraded one(EHP6).

Does anyone have a clue on why the version got changed.

Thanks!