Linked Cubes
A linked cube is based on another cube that is defined and stored on another Analysis server. To end users, linked cubes appear and function like regular cubes. By using linked cubes, you can create, store, and maintain a cube on one Analysis server while the cube is also available as linked cubes on multiple Analysis servers. This arrangement can provide many benefits, including:
- Less overall storage and maintenance is required, compared to storing and maintaining multiple copies of a cube on multiple Analysis servers.
- One organizational unit can maintain ownership of a cube and exclusive update rights but make the cube available to other units as linked cubes.
- Sensitive information can be stored in data sources and cubes on secured server computers but made available through other server computers as linked cubes.
Note You can create linked cubes only if you install Analysis Services for Microsoft® SQL Server™ 2000 Enterprise Edition.
Certain terms are associated specifically with linked cubes. The cube on which a linked cube is based is the
The source cube of a linked cube can be a regular or virtual cube.
When you create a linked cube, do not allow the publishing server and subscribing server to be the same server.
A linked cube always has a ROLAP storage mode and has no aggregations. A linked cube uses the aggregations of its source cube.
The following security requirements apply to linked cubes:
- To create a linked cube, you must have access to the source cube. This access can be provided by including your username in either of the following on the publishing server: the OLAP Administrators group or a cube role for the source cube. If the account does not have access to the source cube, processing the linked cube fails.
- If a linked cube is defined on an Analysis server and Microsoft Windows NT® Integrated Security is used for user authentication, the Analysis server service (MSSQLServerOLAPService) logon account can be either a domain user account or a system account having access to the source cube. However, if a system account is used to create a linked cube, you can still create the linked cube but you will receive a warning if you are not using HTTP or secure HTTP (HTTPS) authentication and the Security Support Provider Interface (SSPI) property in the data source connection string is empty.
- You can also use a data source administered by a Security Support Provider Interface (SSPI) provider such as Negotiate, Kerberos, or NTLM to create a linked cube as long as the account credentials are recognized by the publishing server.
- Data sources using HTTP or secure HTTP authentication are also supported in relation to creating linked cubes.
- If cell security is enforced on a publishing server for a cube, defining a link to this cube is not possible.
In Analysis Manager, a linked cube is identified by the following icon.
In some cases, the dimensions in a linked cube might not be suitable for its end users, but there are features, such as member properties of a dimension, that you can use to resolve this problem. For example, the source cube contains dimensions created for English speakers, but the linked cube is used by French speakers. Or, for example, the source cube contains a Calendar dimension created for universities with four quarters per year, but the linked cube is used by end users at universities with two semesters per year. In cases of different languages among the publishing server and the subscribing servers, you can create member properties on the subscribing server that replace member captions based on the locale ID of the end user's computer. By adding these member properties to a dimension and columns to its table, the dimension can support multiple languages. For more information, see Multiple Language Implementation Using Member Properties.
Before designing linked cubes, consider the following:
- Writeback is not supported in linked cubes.
- Linked cubes cannot be created from source cubes that include shared or private ROLAP dimensions.
- If structural changes, such as adding or deleting measures or dimensions, have been made to a source cube, the linked cube must be reprocessed so that the changes are visible to end users.
- DLLs that contain user-defined functions registered on a publishing server and referenced by the source cube must also be registered on subscribing servers; otherwise they cannot be referenced by the linked cube. Due to maintenance issues, it is not recommended for published cubes to use user-defined functions.
- If a source cube has members with custom member formulas or custom rollup formulas that reference other cubes on the publishing server, then the cube that is referenced on the publishing server must be referenced on the subscribing server. You can make the reference on the subscribing server by creating another linked cube that is based on the cube being referenced in the formulas. This linked cube must have the same name on the subscribing server as the source cube on the publishing server.