The second key Oracle architectural issue the DBA must determine is how many Oracle instances will form the data warehouse for the purpose of loading data? This definition may seem less clear than the previous one regarding queries, but actually it's a much simpler question: Will the data warehouse data be loaded in one step or two?
There are only two options here (shown in Figure 2-4):
Option 1— Load the data from the source directly into the query tables
Option 2— Load the data from the source into a staging area first, then into the query tables