Creating Shared Dimensions

Dimensions are descriptive categories by which the numeric data (that is, measures) in a cube can be separated for analysis. For example, if a cube’s measure is Cost, and its dimensions are Time, Supplier, and Item Description, users of the cube can separate Cost into various categories of Time, Supplier, and Item Description.

A shared dimension is a dimension available to multiple cubes in a database. You should create shared dimensions for common dimensions, such as time, that will be added to multiple cubes.

To quickly and easily create a shared dimension, use the Dimension wizard. The wizard takes you through steps to specify the following definitions for your shared dimension:

• One or multiple dimension tables

  Specify whether the shared dimension will be created from one or multiple dimension tables.

  • One: If you add the shared dimension to a cube, and the shared dimension table joins to the fact table, the cube’s schema type (star or snowflake) is not affected. If the shared dimension table joins to another dimension table, the cube will have a snowflake schema.
  • Multiple: If you add the shared dimension to a cube, its schema type will be snowflake.
• Data source

  Select the data source that contains the tables and columns that define your shared dimension. A data source name identifies a database resource and parameters for its usage. You can select a previously defined data source or specify a new one.

• Dimension table

  Select the dimension table or tables that contain the column or columns you want in your shared dimension. A dimension table is simply a table that contains a dimension. It is a peripheral table joined to a central fact table in a cube’s schema.

• Dimension type

  Specify whether the shared dimension is a standard or time dimension.

• Dimension levels

  Select the levels you want in your shared dimension. Each level is defined by a column (except in some time dimensions). Levels within a dimension are organized hierarchically. For example, in a Location dimension, the levels might be Country, State, and City. The values (that is, members) in each level determine the column and row headings that users see when they browse the cube with a tabular browser. (In graphical browsers, users see other types of descriptive labels produced by the members. For example, each member produces a value on the scale of an axis.)

  If the dimension is a time dimension, and a column with the datetime data type is available in the dimension table, select the column and the levels to create. The wizard parses the column to create multiple levels.

For more information about dimensions, see Dimensions and its subtopics.

To start the Dimension wizard

1. In the OLAP Manager tree view, under a database, expand the Library folder.
2. Right-click the Shared Dimensions folder, point to New Dimension, and then click Wizard.

After you complete the wizard, the Dimension editor appears so that you can further refine the dimension.

You can also use the Dimension editor to update existing shared dimensions.

To display the Dimension editor

1. In the OLAP Manager tree view, under a database, expand the Library folder, and then expand the Shared Dimensions folder.
2. Right-click a shared dimension, and then click Edit.

After you update a shared dimension or its table, you must process it. You can process a shared dimension in two ways:

• Incremental update

  Processes the addition of members (that is, rows) to the dimension table. This method does not process changes to a dimension’s structure or relationships among members.

• Rebuild the dimension structure

  Processes changes to a dimension’s structure such as adding, deleting, or moving a level. This method also processes changes to member relationships such as moving a member from one parent member to another.

Important When a shared dimension is processed with the Rebuild the dimension structure option, all cubes that incorporate the shared dimension immediately become unavailable to users and must be processed before they can be used again.

Caution If a shared dimension’s structure is updated and saved but not processed, it will automatically be processed when any cube incorporating the dimension is processed. At that time any other cubes that incorporate the dimension immediately become unavailable to users and must be processed before they can be used again.

To incrementally update a shared dimension or rebuild a shared dimension’s structure, use the Process a Dimension and Process dialog boxes.

To incrementally update a shared dimension

1. In the OLAP Manager tree view, under a database, expand the Library folder, and then expand the Shared Dimensions folder.
2. Right-click the shared dimension, and then click Process.
3. In the Process a Dimension dialog box, click Incremental update, and then click OK.
4. In the Process dialog box, wait for the incremental update to finish processing or click Stop to halt and cancel processing.

To rebuild a shared dimension’s structure

1. In the OLAP Manager tree view, under a database, expand the Library folder, and then expand the Shared Dimensions folder.
2. Right-click the shared dimension, and then click Process.
3. In the Process a Dimension dialog box, click Rebuild the dimension structure, and then click OK.
4. In the Process dialog box, wait for the rebuild to finish processing or click Stop to halt and cancel processing.

After you process a shared dimension using the Rebuild the dimension structure option, you must process all of the cubes that include the dimension. For more information, see Processing Cubes Using the OLAP Manager.