The Identity tab allows you to select one or more identity fields for the data store.
Identity fields for data stores associates to case stores
When creating an internal database data store that will be associated to a case store, it is required that you specify a set of identity fields for the data store and that you select Identity fields are unique.
Note: When you specify a field as a unique identity field, it needs to have a unique value for each record, otherwise executions using this data store will fail.