Tree may only be joined with Detail record: <PeopleSoft record name>.
You connected or associated an imported tree and a record in an Application Source Qualifier, and the record is not the detail record for the tree.
You can connect or associate an imported tree with a non-detail record if the non-detail record is related to the detail record and you connect or associate the detail record with the Application Source Qualifier.
You can connect the tree and non-detail record to separate Application Source Qualifiers and join them with a Joiner transformation.
To determine which record provides detail data for a tree, open the tree source definition in the Mapping Designer and click the Attributes tab.