IBM Cognos Dynamic Cubes

Chapter 2. IBM Cognos Dynamic Cubes architecture 11

Figure 2-2 shows a cube being started.

Figure 2-2 Starting a cube

Dynamic cubes have many important features and capabilities that are best obtained through

the coordination of database administrators and designers, business intelligence (BI)

modelers, Cognos administrators, and report authors. This section provides an overview of

the various aspects of IBM Cognos Dynamic Cubes in an attempt to show how dynamic

cubes are designed and optimized across a set of coordinated activities.

2.1.1 Dynamic cubes and the data warehouse

A dynamic cube provides OLAP access to a star or snowflake data warehouse to Cognos BI

users. IBM Cognos Dynamic Cubes does not provide support for data warehouses that do not

conform to the star or snowflake topology, nor do they provide access to complex

transactional databases.

The goal of IBM Cognos Dynamic Cubes is to provide quick response to reports and analyses

on large volumes of data. To accomplish that goal, it is important that the queries that are

posed to a relational database conform to a simple set of known patterns that are easily

optimized by relational databases. Star and snowflake topologies are well documented as the

best approach for modeling data warehouses, and are consequently supported by specific

query optimization by nearly all major database vendors.

As with any other relational data source, the database must be defined in Cognos

Administration as a data source, specifically with JDBC connectivity (required for all relational

data sources that are accessed by the DQM server).

12 IBM Cognos Dynamic Cubes

Figure 2-3 shows the data source connection with JDBC connectivity.

Figure 2-3 Data source connection with JDBC connectivity

In addition to a star or snowflake data warehouse, Cognos Dynamic Cubes is able to take

advantage of any relational tables that contain pre-aggregated data that represents the value

of measures from the fact table, summarized by members from one or more dimensions at a

level of aggregation higher than that represented by the fact table. Cognos Dynamic Cubes is

able to route queries for measure values, if appropriate, to these aggregate tables to improve

query performance.