Fill in the missing event that causes deadlock in a database.There are two processes (P1 and P2),each of which needs to update two records (R1 and R2)and the following sequence leads to a deadlock:
1)P1 accesses R1 and locks it.
2)P2 accesses R2 and locks it.
3)____
4)P2 requests R1,which is locked by P1.
A) P2 releases R2.
B) P1 requests R1 again.
C) P1 requests R2,which is locked by P2.
D) P2 releases R1.

Question

Fill in the missing event that causes deadlock in a database.There are two processes (P1 and P2),each of which needs to update two records (R1 and R2)and the following sequence leads to a deadlock: 
1)P1 accesses R1 and locks it.
2)P2 accesses R2 and locks it.
3)____
4)P2 requests R1,which is locked by P1.
A) P2 releases R2.
B) P1 requests R1 again.
C) P1 requests R2,which is locked by P2.
D) P2 releases R1.

Quizplus · Accepted Answer

The missing event that causes the deadlock is P1 requesting R2, which is already locked by P2. This creates a situation where each process is waiting for the resource held by the other, leading to a deadlock. Releasing R2 or requesting R1 again by P1 or releasing R1 by P2 won't resolve the deadlock. Therefore, option C is the best choice.

Fill in the Missing Event That Causes Deadlock in a Database.There