1. CSCI 6315 Applied Database Systems – Exercise (6)
Xiang Lian
The University of Texas Rio Grande Valley
Edinburg, TX 78539

2. Precedence Graph & Conflict Serializable
Given two transactions T1 and T2, please draw the precedence graph and determine whether it is conflict serializable
2 data items x and y, 2 operators read(x) and write(x)
r1(x) means read(x) from transaction T1
The schedule is as follows:
r1(x), r2(y), r1(y), w1(x), r2(x), w2(x), w2(y)
r1(x), r2(y), w2(y), r1(y), w1(x), r2(x), w2(x)
r1(x), w1(x), r1(y), r2(x), w1(y), r2(x), w1(x), w2(y)
If the schedule is conflict serializable, then what is the equivalent serial schedule?

3. Precedence Graph & Conflict Serializable (cont'd)

4. Deadlock Detection T1 T2 lock-X(y) read(y) y=y-50 write(y) lock-X(x)
read(x)
lock-S(y)