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Rebuild for Multi-level Configurations
A multi-level configurable product structure enables the modularization of product structures. Rather than one huge BOM that lists all possible components of a configured variant item, the product structure is divided into sub-assemblies that are configurable themselves and may have their own routings.
For example, as shown in Multi-level Configurations, C1 is a configurable item of the SO Type BOM. C2 is a component of C1 while C2 is also a configurable item itself.

Multi-level Configurations
Here are some scenarios where multi-level configurations are used, including information about how the Configuration Rebuild performs.
Scenario 1: Configurable Sub-assembly
In this scenario, a configured subassembly is selected or created, depending on whether there exists a matching configured variant item.

Configurable Sub-assembly
Item C2, a configurable sub-assembly, has a configurable product structure.
If there is a configuration key for C2, either an existing variant is selected or a new variant is created. As shown in Configurable Sub-assembly, C2-1 is selected or C2-2 is created.
In Configurable Item Maintenance, set Configuration Selection to First Matching or Last Matching, if you want the system to select an existing variant.
In Configurable Item Maintenance, set Configuration Selection to Just Created, if you want the system to create a variant.
If there is no configuration key defined for C2, a new C2 variant, C2-2, is created.
In rebuilding the configuration for C1, the top-level configurable item, the system searches for a matching configuration for C2 according to the configuration key.
If there is a match, the system uses the variant item, attaching it to the product structure of C1.
If there is no match, the system deletes the entire variant product structure and rebuilds the multi-level structure according to the updated configuration and current rule set.
Note: In rebuilding C1, when a matching configuration is found for C2, the system does not run product configuration rules. If there are any rule changes or feature value changes that could cause item data changes, lower-level configurations need to build first.
Scenario 2: Pre-configured Sub-assembly
In this scenario, all C2 sub-assemblies have been pre-configured and each has a configuration attached to it. The pre-configuration can be the result of the Configurator variant item creation process, or can come from Manual Configuration Maintenance, where you manually attach configurations to standard items after item creation. For more information about manually maintaining configurations, see Maintaining Configurations Manually.

Pre-configured Sub-assembly
The system compares the relevant features of the new configuration with the configuration key defined for C2:
If there is a match, C2 sub-assembly is selected.
If there is no match, the system terminates the creation of C1 and reports an error.
In this scenario, the configurable item C2 does not have a configurable product structure since there is no new configured variant item created. C2 serves as a placeholder.
In rebuilding the configuration for C1, the top-level configurable item, the system searches for a matching configuration for C2 according to the configuration key.
If there is a match, the system uses the variant item, attaching it to the product structure of C1.
If there is no match, the system reports an error in the rebuild report.
Note: In rebuilding C1, when a matching configuration is found for C2, the system does not run the Variant Item Data Rule. If there are any rule changes or feature value changes that could cause item data changes, lower-level configurations need to build first.
Scenario 3: Item Number Selection
In this scenario, C2 has a huge number of variations and the possible component items might have very dynamic life cycles. Additionally, the possible component items are standard items not created by the Configurator.

Item Number Selection
Without a configuration key, the actual item wanted is selected explicitly by its item number. Use Variant Item Number Rule Maintenance to set the variant item number as the number of an existing standard item based on a single feature. Typically, an option list or item browse in the Questionnaire is used to manually select the wanted standard item.
In this scenario, C2 does not have a configurable product structure since there is no new configured variant item created. C2 serves as a placeholder.
In rebuilding the configuration for C1, the top-level configurable item, the system searches for a matching configuration for C2 according to the variant item number rule.
If there is a match, the system uses the variant item, attaching it to the product structure of C1.
If there is no match, the system reports an error in the rebuild report.
Note: In rebuilding C1, when a matching configuration is found for C2, the system does not run the Variant Item Data Rule. If there are any rule changes or feature value changes that could cause item data changes, lower-level configurations need to build first.
In Scenario 2 and Scenario 3, C2 serves as a placeholder. A configurable item placeholder can appear multiple times in the product structure, if each placeholder gets the same item. But the system does not support the situation where a placeholder configurable item appears multiple times in the product structure while each placeholder has a different item. The reason is that for a placeholder configurable item, there is only one variant item number rule and one configuration key. If you want different configurable items in the product structure, define different configurable items with configuration keys and variant item number rules.