So, why is someone who normally writes about data warehouses going to talk about Oracle OLAP, and in particular, cube organized materialized views?
I could run out the argument that I work in a BI consultancy and none of us here at Rittman Mead are 100% aligned to a specific expertise area; for example I do OBIEE and OWB as well as data warehouse design and performance. And besides, in my past I did look after one of the largest Oracle Sales Analyzer systems in Europe (ROLAP reporting on a couple terabytes of relational data), so there is quite a bit of Oracle Express Server (and OLAP DML) lurking in my past. But in reality my talk is going to look at the use of OLAP Cube Organized Materialized Views in the context of summary management and that, of course, is right at the heart of what I do!
Summary management has always been one of those ‘art form’ areas of DW/BI – which summary tables to build and how many of them are needed to balance performance, maintenance time and space usage. Query rewrite was great step forward in Oracle 9.2 (OK, it was there before, but I tended not to use it) at last, I only needed to map a single fact table (the base table) into the query tool, and for some third-party tools that was a significant thing. And now with Oracle 11g, the ability to transparently rewrite a query against the base fact table to a OLAP cube is a significant advance, it means that I needn’t think about the materialized views I need create since the cube effectively contains them all! This is a bit of a simplification of course and I will say a lot more in the 50 minutes or so of speaking slot – so if you are Collaborate 08 – and that is just a month away, you could get to hear the whole talk.