Modifying the data model by using Class Manager
The Common Data Model (CDM) is a set of Configuration Item (CI) classes and relationship classes that ship with BMC CMDB. These CI and relationship classes cover most business scenarios. If these out-of-the-box classes do not cover your business requirements, 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.
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 about the following tasks and concepts:
| Task or concept | Reference |
|---|---|
Use Class Manager interface to view the 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 by using Class Manager. Define the class properties in 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 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 by using 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 Class Manager. | Packaging the modified data model by using Remedy Deployment Application |
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
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