XOLAP (extended online analytic processing) is a variation on the role of OLAP in business intelligence. Specifically, XOLAP is an Essbase multidimensional database that stores only the outline metadata and retrieves data from a relational database at query time. XOLAP thus integrates a source relational database with an Essbase database, leveraging the scalability of the relational database with the more sophisticated analytic capabilities of a multidimensional database. Your business needs determine whether OLAP or XOLAP is better suited to your environment.
For information on OLAP, see OLAP Overview.
OLAP and XOLAP store the metadata outline and the underlying data in different locations:
In OLAP, the metadata and the underlying data are located in the Essbase database.
In XOLAP, the metadata is located in the Essbase database and the underlying data remains in your source relational database.
The differences in the locations of the metadata and data are key to understanding how XOLAP can be of benefit as you use Essbase Studio because these differences affect the functionality of OLAP and XOLAP.
OLAP lends itself to traditional relational data storage and data analysis. XOLAP lends itself to operations supported in mixed or “hybrid” environments such as Hybrid Analysis and Advanced Relational Access (familiar to users of Essbase and Essbase Integration ServicesIntegration Services). Many of the basic concepts of Hybrid Analysis and Advanced Relational Access have been folded into the functionality of XOLAP cubes in Essbase Studio.
The workflow of data retrieval in an XOLAP environment is much like that of a non-XOLAP environment:
The model is designated as XOLAP-enabled.
The cube is deployed; however, no data is loaded at that time.
The Essbase database is queried, using Smart View, Oracle Essbase Visual Explorer, or another reporting tool that can access an Essbase database.
Essbase dynamically generates the required SQL to retrieve the data from the source relational database.
See also XOLAP Functionality Guidelines.
XOLAP has several restrictions and several unsupported usages.
XOLAP has the following restrictions:
Although the Outline Editor in Administration Services Console does not prevent you from modifying an XOLAP outline, it is not allowed. XOLAP operations do not automatically incorporate changes in the structures and the contents of the dimension tables after an outline is created. To modify an outline, you must modify the underlying Essbase model and redeploy to a new Essbase database.
Incremental builds for XOLAP-enabled models are not supported.
If you are deploying from an Essbase model that is enabled for XOLAP, it is strongly recommended that you use a new application and database name; or use the Delete all members first option to deploy over an existing XOLAP application.
When derived text measures are used in cube schemas to build an Essbase model, XOLAP cannot be enabled for the model.
XOLAP can be used only with aggregate storage. The database is automatically duplicate-member enabled.
Essbase Studio can create attribute dimensions in Essbase models enabled for XOLAP; however, attribute dimensions must have only one child level.
XOLAP supports dimensions that do not have a corresponding schema-mapping in the catalog; however, in such dimensions, only one member can be a stored member.
User-defined members in an XOLAP model must not have stored parent or children members. The hierarchy must be specified as a dynamic hierarchy.
To compute their values in XOLAP, user-defined members must have valid formulas associated with them.
On the General tab of Essbase Model Properties dialog box, the XOLAP Model option is disabled for models created from dimension server (Performance Management Architect) sources.