Data Warehouses Redux

About a year ago I blogged about my dissatisfaction with Kimball style star schema based DWs. Well, lately I’ve been re-reading Kimball’s books and website and I’m now eating my words.

I guess I can I say this time I get it. This time I see how well conformed dimensions can create a usable DW. I still don’t think it is as elegant as the Inmon style but it can work.

More importantly, I see that the Kimball style DW is the only thing that will get built today. No one is going to get the sponsorship to build a centralized Inmom DW and then the data marts to hang off it. You have to start with the data marts and build the DW up gradually. A Kimball style DW with well conformed dimensions is your only hope. Franky. there are more and more people who try or must build DWs out of “federated” OLTP systems. A Kimball DW is a step up from that.

There is also a performance or latency issue. More and more we want “real-time” DWs or at least reduced latency between the DW and its source. The Inmom style inherantly has more latency becauses it a two step architecture of DW -> DM. If your star schema DMs are also the DW, its one step and less latency.

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