Non Transferable is a property of a [foreign key] link where the link cannot be changed from one parent table record to another.  On Entity Relationship Diagrams, this is shown as a diamond symbol on the link.

[{Image src='ERD_Tranferable.JPG' width='323' align='right' link='attach/Nontransferrable/ERD_Tranferable.JPG'}]

In the example above, the Alias record cannot be altered to point to a different Identity.  That is, the alias is for one person and cannot be switched to another person.

This is managed by a BEFORE UPDATE [data base trigger]