This documentation supports the 23.3 version of BMC Helix CMDB, which is available only to BMC Helix customers (SaaS).

To view an earlier version, select the version from the Product version menu.

Modifying the data model by using Class Manager

The Common Data Model (CDM) is the set of Configuration Item (CI) and relationship classes that ship with BMC Helix CMDB. These CI and relationship classes cover most business scenarios. If the out-of-the-box classes do not cover all that scenarios for your business, you must then extend the data model.  You can extend the CDM by either creating your own classes or extending an existing class with additional attributes.

Related topics

Modification of your data model

Learning about the common data model

Knowledge Article 000095846: Restoring missing common data model attributes from class hierarchy Open link

Retrieving federated data stored externally by creating federated classes

Best practice

Whenever you extend the data model, use your own namespace instead of BMC.CORE. This prevents your extensions from being overwritten by new classes when you upgrade to a future version of the CDM.

Never modify the core CDM class attributes because upgrades across versions overwrite these customizations. Modifications to the CDM, such as changing the attribute field length in a class are not preserved during upgrades.

On the other hand, a new class or an extended class with additional attributes is not overwritten during an upgrade. Creating or extending a class may have a significant business impact and you must perform these modifications only after careful planning and consideration of all eventualities.

This section contains information on the following tasks and concepts:

Do not use Developer Studio to edit any CMDB-related forms, as it might cause data model sync issues.

Task or conceptReference

Use the Class Manager interface to view the CDM and extensions.

Class Manager interface to view CDM and extensions

The purpose of partitions and name spaces in the data model.Partitions and namespaces in the data model

Create or modify classes using the Class Manager.

Define the class properties in the Class Manager, including the type, how the class stores data, and (for relationship classes) the relationship type.

Creating or modifying classes by using Class Manager

Specify permissions for classes. If you do not specify permissions for a class, BMC Helix CMDB assigns default permissions.

Customize the CDM by creating CI and relationship class attributes.

Propagate attributes in a weak relationship to another class.

Specify indexes for a class.
Indexing can reduce database query time.
Configure instance auditing for the class. Auditing enables you to track the changes made to instances of a class.
Common CI relationship class properties you can define when creating a class.Common CI and relationship class properties
Attributes that you can define for classes using the Class Manager.Common class attributes you can define in Class Manager
Different types of audits and options related to them.Auditing overview
Document your data model and its customization be creating an HTML version of your data model.Generating Help for the data model by using the cdm2html utility
Package the modified classes and attributes created in the Class Manager.Packaging the modified data model by using Deployment Application

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