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

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?

Precedence Graph & Conflict Serializable (cont'd)

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