According to the rule 2, he mentioned locking an item, if it is the first data item that a transaction is going to lock, protocol says that we don't need to have a lock on its parent, but if the transaction is going to lock the second item then it looks for its parent to be locked. So here in the example A need not to be locked. Because [subsequent parent needs to be locked]
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Suppose a T1 has locked B ,now suppose again T3 tries to lock B will that be granted?
What is the comparision between 2PL and graph based protocol?
is it possible to perform subsequent locking while the parent has been locked by some other transaction?
It should lock the parent firstly in order to get the lock. so It must wait for the other lock to release the lock.
what about lock on A...as T1 want lock on B..so i think there must be lock on A first then on B..and in the last who will unlock A.? plz explain it.
According to the rule 2, he mentioned locking an item, if it is the first data item that a transaction is going to lock, protocol says that we don't need to have a lock on its parent, but if the transaction is going to lock the second item then it looks for its parent to be locked. So here in the example A need not to be locked. Because [subsequent parent needs to be locked]
If transaction T1 wants to acquire another lock (say L2 ) ,the parent of L2 should be locked by same transaction T1 or not ??????????
Yeah it should be locked by T1 only
how to draw a graph based protocol
what if transaction T4 asks lock on C instead of D?
It will be granted obviously because it is first Intrsuction