2PL guarantees serializability, but it does not prevent deadlocks. 2PL has two phases: growing and shrinking. which of the following rules are used to govern the 2PL protocol?
1
Two transactions cannot have conflicting locks
2
No unlock operation can precede a lock operation in the same direction
3
No data are affected until all locks are obtained i.e. until the transaction is in its locked point
4
All of these