graph based protocol

Question

In Graph based Protocol :-

Why acquireing second  lock on a data item needs to lock their parent data in tree .

please explain

Comments

As in the linked list to access the last node what we follow is:

 We have the address of the first node in the pointer. Therefore, to access the last data item firstly we need to access the first node, first node has address of second node, second node has address of next node and so on. i.e., without accessing initial nodes we cannot access the last node that is why to access any data item we have to lock its parent first. example is B-tree. for more understanding go through B-tree.