I've the following question with an answer and I need your help to clear my doubt related to two phase locking
Question is ;
Consider the following schedule.
w1(a); r2(a); w1(b); w3(c); r2(c); r4(b); w2(d); w4(e); r5(d); w5(e).
Assume that each transaction will commit at the earliest possible point of time soon after completing its last transactions. If the schedule was executed
under two phase locking protocol, write down the locks acquired, released or changed (i.e. ‘Release S(a)’ to indicate release of shared lock for a) including any waiting for locks, commits or deadlocks at each of the times starting at t1.
Given answer is;
My doubt is;
As I know in 2 phase locking we cannot release any locks and then acquire new ones. but in t3 it release the lock and in t4 acquire a lock. Is this correct? If it is wrong please can you help me to find t he answer