Essbase - Aggregate Storage (Enterprise Analytics)

Aggregate Storage (Enterprise Analytics)

Although block storage effectively minimizes storage requirements without impacting retrieval time, it has limitations in its treatment of aggregate data in large applications, motivating the introduction of a second storage engine, named Aggregate Storage Option (Essbase ASO) or more recently, Enterprise Analytics. This storage option makes the database behave much more like an OLAP database, such as SQL Server Analysis Services.

Following a data load, Essbase ASO does not store any aggregate values, but instead calculates them on demand. For large databases, where the time required to generate these values may become inconvenient, the database can materialize one or more aggregate "views", made up of one aggregate level from each dimension (for example, the database may calculate all combinations of the fifth generation of Product with the third generation of Customer), and these views are then used to generate other aggregate values where possible. This process can be partially automated, where the administrator specifies the amount of disk space that may be used, and the database generates views according to actual usage.

This approach has a major drawback in that the cube cannot be treated for calculation purposes as a single large hypercube, because aggregate values cannot be directly controlled, so write-back from front-end tools is limited, and complex calculations that cannot be expressed as MDX expressions are not possible.