Planning to extend the data model

The Common Data Model (CDM) includes classes that describe a wide variety of IT configuration items and their relationships, and some BMC Software products install extensions that add more classes and attributes to the data model. But some IT infrastructures still do not completely map to this model. This section gives recommendations for how to extend the data model in such cases so that you can manage your entire IT infrastructure with BMC Helix CMDB.

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.

Your first step in deciding whether to extend your data model should be understanding the CDM and the extensions supplied by BMC products. Study the BMC Helix CMDB Common Data Model Diagram and BMC Helix CMDB Data Model Help in PDFs-and-videos, and the documentation for BMC products that you own that integrate with BMC Helix CMDB. By reading about the classes that you have, you might find existing classes that serve your needs or at least find the best classes to extend.

This section provides the following information related to extending the data model:

 

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