This documentation supports the 20.02 version of BMC CMDB.

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

Normalization and service impact

In BMC CMDB, you can automatically store the impact details for relationships based on the best-practice impact rules that are shipped with the product. The best-practice impact normalization rules are listed in the Impact Normalization tab of the Mapping Your Data to BMC CMDB 9.1.00 Classes PDF document, available from PDFs and videos. You can also create additional impact rules based on your requirements. For information about creating impact rules, see Creating an impact rule


In CMDB Portal the BMC_Impact relationship class was deprecated to help minimize redundancy in data. The attributes that stored impact information for a relationship are now mapped to the BMC_BaseRelationship class.

The Auto Impact option in the Normalization Engine is enabled for all data sets by default. If you do not want to normalize impact relationships for an individual data set, you can disable the Auto Impact option for that data set. For more information about how to disable or enable impact relationship normalization, see Configuring normalization settings for datasets

The impact relationship rules are created considering the following guidelines:

  • The rules are defined at the relationship class level. The rules defined for the class are applied to every instance of the relationship class that you create.
  • The rules are defined in BMC CMDB depending upon the source class, destination class, and the relationship class itself.
    For example, for the BMC_HostedSystemComponents relationship class, BMC_ComputerSystem source class, and BMC_DiskDrive destination class, a rule is defined to set the HasImpact attribute to Yes and ImpactDirection attribute to Destination-Source. This rule is defined to indicate non availability of a system due to a hard drive failure.
  • The rules apply to all data sets in BMC CMDB. You cannot configure a separate rule for each data set.
  • When rules are set for a relationship class at both parent and child class levels, the child class rule overrides the parent class rule.
  • Apart from the regular attributes that are automatically set on the relationship, source, and destination classes, you can also specify additional qualification strings. In such cases, the qualifier is used to determine whether the impact attributes should be applied on the CI that is being processed.
  • The rules eliminate duplicated impact relationships by merging them into one relationship, when any two given endpoints are impacting each other in one direction or another. If the Merge process finds any matching Impact relationships when the rule is applied on a relationship instance, the impact relationships are merged. The rules merge those instances of the BMC_BaseRelationship class that have the same values for the Name, HasImpact, ImpactPropagationModel, ImpactDirection, and ImpactWeight attributes.

If you update the values of the HasImpactImpactDirectionImpactWeight, and ImpactPropagationModel attributes of a relationship instance and then run the normalization job, the Normalization Engine retains the modified values for these attributes by default. However, you can configure the Normalization Engine to reset the values of these attributes based on the best-practice impact normalization rules, each time you run a normalization job. For information about configuring the Auto Impact Manual Edit setting, see Configuring normalization settings for datasets.

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