This chapter provides information about customizing the access layer of Oracle Communications Data Model.
The access layer of Oracle Communications Data Model provides the calculated and summarized ("flattened") perspectives of the data needed by business intelligence tools. Access layer objects are populated using the data from the foundation layer 3NF objects.
The access layer objects in the ocdm_sys schema include: derived and aggregate tables and OLAP cube views. This layer also contains data mining models. The results of these models are stored in derived tables. The models themselves are also defined in the ocdm_sys schema.
When designing and customizing access layer objects:
Aggregate Tables in Oracle Communications Data Model
Aggregate tables are tables that aggregate or "roll up" the data to one level higher than a base or derived table (and other functions can also be in the aggregate tables such as average, count, min, max, and others).
Dimensional Components in the Oracle Communications Data Model
There is often much discussion regarding the 'best' modeling approach to take for any given data warehouse with each style, classic 3NF and dimensional having their own strengths and weaknesses. It is likely that data warehouses must do more to embrace the benefits of each model type rather than rely on just one - this is the approach that was adopted in designing the Oracle Communications Data Model.
Materialized Views in the Oracle Communications Data Model
Materialized views are query results that have been stored or "materialized" in advance as schema objects. From a physical design point of view, materialized views resemble tables or partitioned tables and behave like indexes in that they are used transparently and can improve performance.