Question

  There are two sites s1 and s2 and three transactions T1, T2, T3.

The time table is as follows

                           S1                                           S2

t1:             (T1, W, a)                                      (T3,W, b)

      t2:             (T2, R, b)                                       (T1, R, b)

      t3:             (T1, R, a)                                      

      t4:                                                                    (T2, R, c)

      t5:                                                                    (T3, R, c)

     Is there any deadlock in this distributed processing? Why?

Answer 1

Given problem :

	S1	S2
T1	T1,write,a	T3,write,b
T2	T2,read,b	T1,read,b
T3	T1,read,a
T4		T2,read,c
T5		T3,read c

Distrubuted deadlock :

• t1: T1 initiated at site S1 and creating agent at S2

• t2 : T2 initiated at site S1 and creating agent at s2 for T1

• t3 initiated with reada with T1

• t4 : reading T2

• t5 : reading T3

Here only T1 seems to have deadlock. However there is no deadlock occurring overall

               Because nothing is forming a loop and the resource is not in waiting process. Hold and wait doesn’t result in distributed deadlock .