Multilevel master-detail relationships
Key Takeaway
In a multilevel master-detail relationship, the master record at the top controls deletion, ownership, and security for every record below it.
A master-detail relationship closely links objects so that the master record controls certain behaviors of its detail records. A multilevel master-detail relationship extends that control down to subdetail records, so you can perform operations across the master, detail, and subdetail records together.
How a multilevel setup is structured
You define relationships by creating custom relationship fields on an object. In a multilevel setup, the master controls the detail, and the detail's own subdetail records follow the same master.
For example, imagine a chain of three objects: Account is the master, Expense Report is the detail, and Expense Line Item is the subdetail.
To create multilevel master-detail relationships, you need the "Customize Application" user permission. The master object can be a standard object, such as Account or Opportunity, or a custom object.
On the user interface side, the master-detail relationship field (the field that links the objects) is required on the page layout of both detail and subdetail records.