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Define or edit data source precedence rules

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Define or edit data source precedence rules

If multiple data sources are authorized to update the same table or the same table attributes in the CMDB, assign a priority to each of these data sources to prevent them from overwriting each other's updates. Without data source precedence rules, data sources can overwrite each other's modifications.

Before you begin

Role required: itil has read access, itil_admin (on top of itil) has full access.

About this task

Data source precedence rules are used along with data refresh rules and reconciliation rules to determine reconciliation steps for a CI. These rules determine if, when, and by which data source a CI can be updated.

After an authorized data source updates an attribute, subsequent updates are accepted only from the same data source or from a data source with a higher priority. Updates from a data source with a lower priority are rejected, unless these two conditions are met:
  • A higher priority data source previously updated the CI attribute.
  • The CI became stale based on data refresh rules for the CI class.

Information about the last data source that updates each attribute is stored in the Data Source History [cmdb_datasource_last_update] table.

Data source precedence rules affect reconciliation of stale CI attributes. During reconciliation, the information in the Data Source History table is considered along with the data refresh rules for the CI's class, to determine if a CI attribute is stale. A CI attribute is determined to be stale if it was not updated by the latest data source to update the CI, within a time period. The time period is specified by the Effective Duration time in the data refresh rule for the class for the data source. In this case, if another authorized data source, with a lower priority attempts to update the stale CI attribute, the update is allowed.

Note: Users with the itil role have read access to the CI identification rules.


  1. Navigate to Configuration > CI Class Manager.
  2. Click Hierarchy to display the CI Classes list. Select the class for which to create a data source precedence rule.
  3. In the class navigation bar, expand Class Info and then click Reconciliation.
  4. In the Data Precedence Rules section, click Add to create a rule or select an existing rule to edit. Fill out the details in the Create Precedence Rules dialog box.
    Field Description
    Data source The data source that this precedence rule applies to. EventManagement, ImportSet, ManualEntry, or an application such as Tivoli are examples of a data source.
    Priority Priority of this precedence rule within the set of precedence rules for the specified table. Smaller numbers designate higher priority. Data sources without a precedence rule are assigned the lowest priority.
    Active Check box to activate this precedence rule.
  5. Click Save.