We need to understand why we need intention locks. Here, suppose we do

not use intention locks, and only use S and X lock modes. We can change

R$-3$ to be $$Transaction Ti can lock a node Q in S mode only if Ti currently

has the parent of Q locked in either X or S mode,$$ and change R$-4$ to be

$$Transaction Ti can lock a node Q in X mode only if Ti currently has the

parent of Q locked in X$.$ Given the original rules and the rules modified,

explain why we need intention locks and show intention locks improve

concurrency.

$($b$)$ Consider the rules with intention locks. Can we change R$-2$ and allow a

transaction Ti to start locking at any node in the hierarchy? Give your

answer with explanation using examples.

$($c$)$ By the R$-6,$ the protocol unlocks from the bottom of the hierarchy. Ex$-$

plain if it is okay if the protocol unlocks from the top of the hierarchy

instead, using examples.