Consider the database transactions listed below.

T$1$

a $=$ read$($x$)$

c $=$ read$($y$)$

write$($z$,$a$+$b$)$

commit

T$2$

a $=$ read$($x$)$

write$($y$,$a$+1)$

commit

T$3$

c $=$ read$($x$)$

write$($x$,$c$+1)$

write$($z$,$c$+2)$

commit

Assume that the initial values of the persistent data items x$,$ y and z are the following:

x $=2,$ y $=0$ and z $=2.$

Show a sample concurrent execution of the transactions T$1,$ T$2,$ and T$3$ that is NOT

conflict serializable.

Prove that the execution is NOT conflict serializable.

To prove that the execution is NOT conflict serializable use a technique of two$-$dimensional diagrams presented to you.