No of BW Source systems and BODS Datastores

Hi Experts ,

BODS 4.2 SP1 and BW 7.4

I'm creating BW and BODS integration , where BW is source and target.

We have multiple UD and DB connections in BW , we are planning to change the data extraction via BODS.

I encountered some doubts,

do we need to create one source system for each Database in BW ?

or proceed without specifying source data store.If yes how to do ?

How to create jobs to import data to BW from SQL server and oracle?

Thanks in advance.