Which of the following transaction(s) follow 2-phase locking protocol?
1. Only 1
2. Only 2
3. Only 1 and 3
4. None of them
In 2, we are doing like
Lock, Lock, Unlock, Lock
we can't do unlocking in between ..
Read : http://www.mathcs.emory.edu/~cheung/Courses/554/Syllabus/7-serializability/2PL.html
in 2, there is no "Lock, Lock, Unlock, Lock"
lock1 and unlock2 are on two different transactions T1 and T2..
only 2 is allowed under 2PL.