Checking for multiple different configurations of a component (detecting component skew)

Component skew occurs when multiple different configurations of a component are in the same configuration hierarchy. Configuration leads or administrators in the Global Configuration Management (GCM) application can help determine whether skew is intentional and fix skew as needed.

About this task

Component skew occurs when different configurations of a component are in the same configuration hierarchy. Both global and local components can have skew. A global configuration typically contains local configurations, so skew in the first likely means skew in the latter. Because local configurations contain versioned artifacts, if you don't examine and possibly resolve skew, you might end up with the wrong artifact versions in a configuration hierarchy. When you see a warning message about skew in the hierarchy, examine the details and run a skew report as described in the Procedure section.

If there are multiple different local configurations from IBM® Engineering Lifecycle Management (ELM) applications, the GCM application resolves to the configuration that is ordered first. Two situations might occur.
  • Users might not see the local configuration that they expect in their Current Configuration menu.
  • Users might not get the results they expect in the local configuration (wrong artifact versions are selected in ELM applications).

See Unexpected local configuration in Current Configuration menu for more information.

Alternatively, component skew does not always mean that there is a problem. Sometimes component skew is intentional. The following example illustrates both intentional and unintentional skew, and what you can do in each case.
  • Component skew occurs unintentionally when an extra or wrong configuration is added to the same component. In the following Car example, your team working on the parking assist camera, which uses Camera - Model A - v2.0. The team working on the adaptive cruise control uses a more recent version, Camera - Model B - v3.0. The teams didn't work together to achieve consistency across the car.

    Example of unintentional component skew, with warning icon

    The following component skew report shows that multiple different configurations of the Camera component are in the parking assist and adaptive cruise control components of the car. If the car architects and the procurement teams decide that the skew is unacceptable, they might insist that both teams use the same version of the camera in their systems. To fix this unintentional skew, a configuration lead can open the tree view and replace one of the camera global configurations with the correct global configuration.

    Example of component skew report

  • Component skew occurs intentionally when it's necessary to use different configurations of the same component. Continuing with the Car example, if the car architects decide that different camera versions are needed to satisfy different requirements for each system, then skew is acceptable and no action is needed.

The previous examples are simple to illustrate points. Typically, you will run a component skew report after you build a large, complex hierarchy, or use it as a diagnostic tool if users report that the wrong local configuration is displayed in the Current Configuration menu or wrong artifact versions are selected in ELM applications.

In the report, use the Configuration and Location columns to determine which configurations to replace or remove to fix unintentional skew.

Local configurations: Order and preferred configurations

In a skew report, use the Order column to understand which of the multiple different configurations is the preferred, or highest precedence, configuration of that component.

When you click the preferred configuration, links to artifacts across applications resolve and your configuration context is set to the global configuration in the tree where skew doesn't exist for that configuration. Using the preceding skew report as an example:
  • The Camera - Model A - v2.0 baseline Requirements Management (RM) baseline is first in the sort order, so it has highest precedence. When you click that baseline, it opens in RM and your configuration context is set to the Car global configuration. You can see links from artifacts in that baseline to artifacts in other applications.
  • The Camera - Model B - v3.0 baseline RM baseline has lower precedence. When you click it, it opens in the RM application, but no global configuration context is set, so you cannot view and create links to artifacts in other applications. To do this, you must you must manually set the configuration context to a global configuration: choose a global configuration that is lower in the tree than Car - either Adaptive Cruise Control or Parking Assist. You can't choose Car because the preferred RM configuration, Camera - Model A - v2.0 baseline, resolves to Car.

If the order of configurations is not what you expect, discuss the order with a configuration lead or GCM administrator.

Component skew in nested configurations

Contributions from IBM Engineering Workflow Management (EWM) source control management (SCM) and IBM Engineering Systems Design Rhapsody® - Model Manager (RMM) often contain nested local configurations from the same application. A GCM administrator must configure the GCM application to detect component skew across these nested contributions. Otherwise, nested contributions appear in the hierarchy, but skew across the nested contributions is not detected.

Example

The following image shows an example of component skew in contributions from EWM SCM. In this example:
  • The Car stream contains component skew: it contains multiple different streams of the same camera component.
  • The camera global streams contain different EWM snapshots.
Image showing component skew in an EWM SCM contribution in a configuration hierarchy
In this example, a configuration lead might decide that the skew is not intentional, and repair skew by replacing the EWM Camera - Model A - initial snapshot with the EWM Camera - Model B - R1M1 snapshot.
Note: In this example, skew in the EWM snapshots would have also been detected in version 6.0.5, but only for the Camera - Model X configurations. Starting in version 6.0.6, the component skew report also indicates that the EWM Web UI, Java UI, and Prerequisites baselines are in skew.

In other scenarios, you must decide whether to keep the skew because it is intentional, or to remove or replace one of these nested local configurations to remove the skew. For example, you might want to replace the configurations in skew with more recent streams or baselines.

Procedure

  1. Select a configuration in the tree view, right-click, and select Detect Component Skew.
  2. View the report. It shows the multiple streams and baselines of the component for the selected configuration, if they are different.
  3. Find other configurations that use the multiple different streams and baselines by looking under the Location column in the results table.

    The report shows where the selected configuration exists in relation to the current configuration where the report was initiated. Skewed configurations that are in unrelated configurations are not listed. Use the report to find which global configurations to remove or move.

  4. Check for component skew again, after you replace or remove all the unnecessary configurations or move a global configuration to reorder the report list.

    If the report shows that there is no component skew or that the order is now correct, you are done.

    If the report shows multiple different configurations where there should be none, then click Find Where Used for each configuration. Replace or remove each unnecessary configuration.

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