There is no set rule...and you dont need separate "instances" for each..just schemas. the DAC/INFA metadata is fairly small so you can put them together if you want but OBAW is usually created in its own separate instance since the maintenance may be different. It really is a question for your DBA team. Suppose you need higher availability for certain instances, or if there is maintenance windows where you need the OBAW DB separate from INFA..or if you are using the INFA rep for populating other systems, you may not want to group it with OBAW. These are some things to consider.