Bruce W Cassidy (2/17/2014)
Something to be aware of is that an ODS is often "operational" (which usually means it has an up-time requirement of 24x7), and for that reason it can make an excellent part of the DW to serve as an interface to other systems.
Correct! I see the part of the term "operational" as the "of the operational (source) system".
If you source system is a flat file, for example, the ODS for is could well be a wide table representing this file, or a few tables, which can represent the content of the same file. Decision of how to populate the ODS should be taken by the DW developer. Some of such decisions could be a "dump" (replicated database, restored backup), or a selective tables dump, or a group of tables, which provides the same data as the operational system contains.
There's even a form of the ODS that's actually extracted from data marts (rather than the other way around)!
Strange... I was trying to imagine when and how this could be the case.
Data Marts are usually populated from the DW (Inmon or Data Vault), or form the DW (Kimbal model).
But is the DW populated from the source systems anyway? Why could not we populate the ODS from the source system? What about the recency of information in such ODS? Once a day? Why do we need such ODS?
M.Sc.IT, M.B.A, MCTS BI 2008, MCITP BI 2008, MCTS SQL Dev, CSM, CDVDM