Reparenting detail records in a master-detail relationship
Key Takeaway
Master-detail relationships block reparenting by default, so an administrator must select "Allow reparenting" before detail records can move. After a detail record moves, its owner and its access come from the new master record.
In a master-detail relationship, each detail (child) record is tied to a master (parent) record. The master record controls certain behaviors of the detail record. Reparenting means moving an existing detail record to a different master record. Because the master decides who owns a detail record and who can see it, a move also changes the detail record's owner and access.
How a master-detail relationship works
A master-detail relationship links objects closely, so the master record controls certain behaviors of its detail and subdetail records.
An Account can be the master of an Expense Report. The Expense Report is in turn the master of an Expense Line Item. The Expense Report is a detail record of the Account. The Expense Line Item is a subdetail record.
Every detail record must have a master record. The master-detail relationship field is required on the page layout of detail and subdetail records.