Creating precedence sets and associations for reconciliation merge activities

BMC CMDB includes standard identification and precedence rules for setting precedence values for datasets, classes, or attributes before running a reconciliation merge activity. 

A configuration manager can create a custom precedence set with custom precedence values at dataset, class, and attribute levels if the standard rules are not suitable.

Precedence sets and values

A precedence value determines the data that is written to the target dataset from the source datasets. A precedence set defines the precedence value for a dataset in a merge activity. Each source dataset is paired with a precedence set. This set serves as the default precedence value for all classes and attributes in that dataset. If precedence value is not specifically assigned, the classes and attributes in a dataset carry the value set at the dataset level.  When the merge activity runs, if the dataset value and the class or attribute value are not the same, the precedence value assigned at the attribute level is considered. Class-level precedence values apply to all attributes of the class. By default, the dataset precedence value is 100. You can change the precedence values for classes and attributes to override the value set at the dataset level and class level.

The following image shows how precedence values determine the data that is populated into the production dataset during a merge activity. 

Specifying precedence values to attributes while merging datasets

Precedence values do not apply to the core attributes. 

Precedence associations for reconciliation merge activities

A precedence association links a dataset with a precedence set and can be reused among merge activities.

Each merge activity is linked to one precedence association that determines the precedence for each dataset that participates in the activity.

The following figure shows a sample list of existing associations that you can choose from for a merge activity.

Setting the merge precedence when reconciling multiple datasets to a target dataset

When you merge the data from multiple source datasets into a target dataset, you can select the classes and attributes from a source dataset that can be merged.

To set the merge precedence for merging datasets

1. In the CMDB UI, select Configurations > Manage Reconciliation Rules > Precedence Exceptions.
   
   
   
2. To create a new precedence set, click Add Precedence Set.
3. Select the dataset to create a merge ruleset and set the precedence values.
   
   
   The precedence set area is displayed on the screen.
   
    

4. In the Precedence Set  area, enter the required information in the following fields.

   Merge Ruleset Name	Type a unique name for the precedence set. The name cannot contain any characters that are not allowed in file names for the operating system of your server. For example, on a Windows server, your job name cannot contain the following characters: \ / : * ? " < > |.
   Merge Order	When multiple source datasets have the same precedence value, the Merge Order value determines the dataset that is merged to the target dataset. The lower the value of the Merge Order, the higher the priority for that dataset. You can assign values starting from 0 (Zero).
   Explicit Precedence	Select this option to apply explicit precedence entries for classes and attributes. You must add precedence rules for the classes and attributes. Clear this option to apply this precedence set to all classes and attributes for which a precedence is not defined.
   Ignore If Null	Define how to handle empty, or NULL, attributes in the dataset associated with the precedence set. The Ignore if Null setting at the precedence set level is overridden by the same setting in any precedences defined for the set. Note: This field is visible for custom jobs and not for standard jobs. Checked — If the value of an attribute in this dataset is NULL and the precedence value for this dataset is the highest, the merge activity ignores the dataset. NULL value is not written to the production dataset. Cleared — Applies the precedence value for this dataset regardless of whether an attribute value is NULL. Warning: If used incorrectly, Ignore if Null can cause instances that cannot be deleted.
   Precedence Value	Enter or select a value for the dataset that uses this precedence set. Assign a value from 0 through 1000, inclusive, with higher numbers meaning a higher priority. The precedence value is overridden by the value in any other precedence defined for the set.
   Class	Select the class to which the precedence value must apply.
   Attribute	If the precedence is for an attribute, select it from the Attribute list and enter a precedence value.
   Status	Select Active to ensure that the precedence value is considered for the merge activity. You can later disable the activity by changing it to Inactive.

5. After adding the precedence values, click Save to save the merge ruleset for the selected dataset.

Similarly, you can set precedence values for multiple datasets within a precedence set.

You can now relate the precedence set to a dataset by creating a precedence association.

To associate a dataset with a precedence set for merging datasets 

1. In the Precedence Exception area, click Select Association Set, and select a Precedence Set from the list.
   
2. View, create, or edit the merge ruleset for any of the datasets in the precedence set edit area.
    
3. If you make any changes to values in the selected precedence set, click Save to save your changes.

Where to go from here

Creating a reconciliation job