Building Service Models › How to Build a Service Model › Create a Propagation Policy with Custom Propagation

Create a Propagation Policy with Custom Propagation

Custom propagation requires you to specify when and how to change the severity of a parent item. The severity of the parent item changes based on the impact value of the children items.

Custom propagation policy is useful in situations when the impact of dependent CIs is complex. For example, a web server farm may have several servers that perform the same role. This redundancy means that a fault condition on one device may not impact the availability of the service. In fact, several servers may need to fail before users experience service degradation.

A sample rule is "If 50% of the servers are down, propagate an impact of Moderately Degraded. If 75% are down, propagate an impact of Severely Degraded." The default custom propagation policy contains the following rules:

• The first rule sets the parent item impact to Slightly Degraded when any of the included items have an impact greater than or equal to Moderately Degraded (20).
• The second rule sets the parent item impact to Moderately Degraded when any of the included items have an impact greater than or equal to Severely Degraded (30).

Note: When you assign custom propagation policy to a CI and the threshold is reached, the target CI attains the specified severity value and an infrastructure alert with the appropriate severity. However, because the alert applies to the CI as it relates to the parent service, the CI icon does not change color as expected, and the severity propagates to a separate impact calculation on the service, which is reflected in the service icon color.

You can change the default custom propagation policy. The Service Modeler must be closed to change the default custom policy.

Note: CIs in maintenance mode are excluded from custom policy calculations related to average or percentage.

In the Service Modeler, you define custom policies that are specialized for individual relationships. A service can have multiple custom propagation policies, and a custom propagation policy between CIs can have up to four rules for propagating impact.

Follow these steps:

1. Create a new service or modify an existing service.

   The Service Modeler opens.

2. (Optional) Create a group if you have multiple configuration items that will have the same policy.
3. Right-click a parent object or group that has custom propagation and select Define Policies, Custom Policies, Edit.

   The Policy Editor dialog opens.

4. (Optional) Select the Automatically Maintained check box to automatically change the relationship to Is Affected By or Is Evolution Of and apply the custom propagation policy when new CIs are added to a group that uses custom propagation. Auto-maintenance applies to relationships added by both manually editing a service and through automation by service discovery or service import.

   Note: You can set Automatic Policy Maintenance for the Modeler operation to on by default in the Set Preferences dialog.

5. Select one of the following from the Policy Type drop-down list:

   Average

   Sets the impact of the parent item based on the average impact values of CIs associated with the policy.

   Percentage

   Sets the impact of the parent item based on a percentage of CIs that have the impact specified in the rule.

   Any

   Sets the impact of the parent item when any CIs associated with the policy have the impact specified in the rule.

   All

   Sets the impact of the parent item when all CIs have the impact specified in the rule.

   Default: Any

   The text of the rules on the dialog changes to reflect the selected policy type.

6. Complete the following fields and settings for each rule that you want to create:

   % of items

   (Percentage type only) Defines the percentage of items that must exceed the impact threshold to meet the rule criteria.

   Threshold

   Defines the impact threshold. The appropriate amount of CIs (as defined by the policy type) must meet or exceed the impact threshold to meet the rule criteria. Define a number between 0 and 40. The impact numbers translate to the following impacts:

   • 0: Operational
   • 1-10: Slightly Degraded
   • 11-20: Moderately Degraded
   • 21-30: Severely Degraded
   • 31-40: Down

   Set Severity

   Defines the severity to assign to the parent item if the rule criteria are met.

   The text for each rule changes to reflect the new settings. Define as many of the four available rules as the policy requires.

7. Select the entities to which to apply the policy. Use the arrows to move CIs from the Available Configuration Items pane.

   All items included in the policy appear in the 'Configuration Items Included In Policy' pane.

8. (Optional) Click the 'Create a new policy' tab and create a different policy for any items that were not included in the current policy.
9. Click OK.

   The policy or policies are associated with the specified items. You must save the service to save any created policies.

Any custom policies that you define appear in the Policies tab in the pane below the service topology. You can right-click existing custom policies to edit or delete them. You can edit one custom policy at a time and delete multiple custom policies at the same time.

Note: Only custom policies that you have created appear in the Policies tab, not the defaults.