Organization of the OLAP Catalog

The repository for OLAP metadata is known as the OLAP Catalog. This repository is included by default with the Enterprise Edition of the database when installed with either the General Purpose or Data Warehouse configuration.

The OLAP Catalog is one component of Oracle OLAP. The other server-side components are the OLAP calculation engine and support for analytic workspaces. On the client side, Oracle OLAP includes the OLAP API, an API for developing OLAP client applications in Java.

CWM and CWM2

The OLAP Catalog, owned by the OLAPSYS user, contains two distinct metadata repositories each with its own set of APIs:

• The CWM metadata repository, first released with Oracle 9i Release 1, is still supported in the current release. The CWM metadata repository, based on CWM Lite (Common Warehouse Metadata) is used by Oracle Enterprise Manager. You can create and view CWM metadata by using Enterprise Manager's OLAP Management feature.
• The CWM2 metadata repository, newly available with Release 2 (9.2), provides support for additional warehouse configurations. You can create and view CWM2 metadata by using the CWM2 PL/SQL packages and views.

Both metadata repositories include the following:

• Metadata model tables - A set of tables that instantiate the OLAP metadata model. These tables define all the OLAP metadata objects: dimensions, measures, cubes, measure folders, and so on. Within the metadata definitions are references to the actual warehouse data. The CWM model tables are named with the CWM prefix. The CWM2 model tables are named with the CWM2 prefix.
• A Write API - A set of PL/SQL packages for creating and editing OLAP metadata. These packages contain procedures for inserting, updating, and deleting rows in the model tables. The CWM packages are named with the CWM prefix. The CWM2 packages are named with the CWM2 prefix.
• A Read API - A set of SQL views providing information about the metadata registered in the model tables. The CWM views are named with the OLAP prefix. The CWM2 views are named with the OLAP2 prefix.

CWM2 additionally includes Preprocessors, PL/SQL packages for transforming certain types of warehouse data to a format supported by the CWM2 APIs. Preprocessors are available for data stored in analytic workspaces and for parent/child dimension tables.

Depending on the organization of your warehouse and the needs of OLAP clients, you can use CWM metadata or CWM2 metadata, or some combination of both.

Important: You cannot create or view CWM2 metadata from Enterprise Manager's OLAP Manager. Conversely, you cannot create CWM metadata using the CWM2 APIs. However, CWM2 includes a set of union views that allows you to view the OLAP metadata in both the CWM and CWM2 model tables. A separate set of CWM2 views allows you to view metadata that directly represents objects in analytic workspaces.

Logical Steps for Creating the Metadata

Whether you create OLAP metadata programmatically (CWM2) or by using Oracle Enterprise Manager (CWM), you follow the same logical steps.

To create OLAP metadata:

1. Create the dimensions. Specify the levels, attributes, and hierarchies associated with each one.
2. Create cubes and specify their edges (dimensions).
3. Create measures that represent the fact data. Associate each measure with a cube.
4. Map the metadata entities to the source data.
5. Create measure folders in which to store related measures. Populate the folders with measures.