When is delta recorded in ECC from SAP BI

Hi,

Have a basic question, When is delta timestamp recorded in ECC from SAP BI:

A) When Data (Delta request) is received in BI PSA Or

B) When Data (Delta request) is updated in one of the target from PSA?

Is it different in BI7 and BW3.x?

Scenario: If I am getting complete data in one DSO (1st layer) from a standard BI Content extractor, can I divide that DSO in multiple DSOs (based on year/region using semantic partitioning) without disturning the delta associated with that extractor?

Thanks,

Bharat