A server manages the objects a1, a2,... an. The server provides two operations for its clients:

read (i) returns the value of ai;
write(i, Value) assigns Value to ai.
The transactions T and U are defined as follows:
T: x= read (j); y = read (i); write(j, 44); write(i, 33); U: x= read(k); write(i, 55); y = read (j); write(k, 66).
Give three serially equivalent interleavings of the transactions T and U.

The interleavings of T and U are serially equivalent if they produce the same outputs (in x and y) and have the same effect on the objects as some serial execution of the two transactions. The two possible serial executions and their effects are:





We show two examples of serially equivalent interleavings: