In Appian, when dealing with a record type that has data sync enabled and is backed by a database table, changes to the structure of the underlying data model, such as removing a field, should be carefully managed. The correct approach involves deleting the unused field from the Custom Data Type (CDT) that defines the structure of the data for the record type. Following this change, a full resynchronization of the record type is necessary to ensure that the changes in the CDT are reflected in the record type and its associated data in Appian. This process ensures data integrity and consistency across the application and the database. Reference:

Appian Documentation on Data Management: Provides guidelines on managing data structures, including CDTs and record types, within Appian applications.