PRPC Version: 7.1.8

I don't see foreign key references in pega database OOTB relations. There is a foreign key label in ERD but not the foreign keys and reference tables in DDL(https://pdn.pega.com/sites/pdn.pega.com/files/legacy/DevNet/PRPCv5/KB/images/24260Relationship3FULL.jpg). It seems all the transactions handle in PRPC application layer. Is this the expected behavior of PRPC? What pega suggests to design to ER while working with database? (Same as OOTB design or different approach)

Why am I asking is, we are working on health care domain project and designing ER diagram with plenty of tables. We have below doubts.

If we design ER to handle transaction constraints in database end it is difficult to handle insert, update, delete transactions from application layer which means obj-Save, rdb-Save operation sequence handling is difficult. With this approach how we can roll back if somthing goes wrong.

If we design ER same as PRPC OOTB ER, we can handle all the transaction from application end.

What is the best approach? Please let us know advantages and disadvantages as well.

Thanks in advance