Optimistic Lock and Exclusive lock BOPF

Hello Experts,

I have created a BOPF Application with one ROOT and ITEM.

If i create a ROOT Entity data , then i need to lock it before creating ITEM. Optimistic Lock and Exclusive lock are two options coming while locking the ROOT.  . When i checked from two different sessions here is what i observed.

1st session :  I opened Root data in one session, put a Optimistic Lock . Entity came in editable mode :

2nd session : I opened the same root data and put a Exclusive lock. Again the data came in Editable mode.

Now the same data is opened by 2 users, editing it and Lock concept is not happening here.

How to lock the Root via Coding in BOPF. While consuming BOPF, How to Lock a Root data to ensure that no other can lock it. ? ?

Please provide your inputs with some code snippets.

BR,

Nikhil Kulkarni