DB2 - exercize session 01

27 October 2015

Concurrency Control

View-Serializability VSR

Material on cs.unibg.it/mutti/

If we have the same final writes and read from of a serial schedule

A read-from means that the same object x was already written by another transaction, different from the one whic is now reading x.
A final-write means that the object x is written and there are no others transaction

Exercize:

Classify the following schedules as non-vsr, vsr or csr.

r1(x) r2(y) w3(y) r5(x) w5(u) w3(s) w2(u) w3(x) w1(u) r4(y) w5(z) r5(z)

x	r1	r5
y	r2	w3
u	w5	w2
s	w3
z

Blind writes

A write is said to be blind if it is not the last action of resource X and the following action on X is a write wj(x)