Define Source Systems > Introduction to source systems
Introduction to source systems
A source system is an asset that acts as a data source for the Business 360 data store. The source system asset helps business users track the source of a record. For example, records from Salesforce and Workday can contribute to master records.
You can use predefined source systems or create custom source systems.
When you ingress or import data, MDM SaaS standardizes the reference data. To standardize the reference data, associate picklists of a business entity with the reference data custom code lists from MDM - Reference 360.
For more information about adding picklists to a business entity, see Add a picklist.
For more information about code lists and crosswalks in MDM - Reference 360, see Code lists and Crosswalks.
The associated code list contains code values, and the crosswalks of the associated code list contain value mappings. When you import data, Business 360 checks whether the code list that you associate with a picklist has a crosswalk with value mappings. The import process standardizes the values of the picklists with the mapped values in the associated code list. If a crosswalk isn't available, the ingress process fails in the transform step.
If the reference data in MDM - Reference 360 contains both Enterprise and custom code lists, MDM SaaS lists only the custom code lists. MDM SaaS doesn't display the Enterprise code lists because standardization of picklist values requires a crosswalk with value mappings between the Enterprise and custom code lists.
You can't delete a code list in MDM - Reference 360 that's associated with a picklist of a business entity. Additionally, you can't delete a crosswalk in MDM - Reference 360 that contains value mappings of custom code lists associated with the source systems.
When you associate a picklist to a code list from MDM - Reference 360 in organizations created after the October 2025 release, MDM SaaS considers the picklist value even if the value isn't available in the associated code list. However, the record is treated as invalid.
In organizations created after the October 2025 release, MDM SaaS loads records with picklist values that aren't available in the associated code list during ingress or file import. However, these records are marked as invalid in business applications.