Operational Laws
Let,
N: Number of users
X: Transaction throughput (in transaction/sec)
R: Transaction response time (in sec)
S: Service Demand (in sec)
Z: Think time (in sec)
U: Utilization of the resource (% of time the resource is busy)
Then,
The Utilization Law: U=X*S; facilitates the computation of the service demand.
Little's Law: N=X*(R+Z); Little's Law check is mandatory even before we look for bottlenecks in the application as this validates the test bed. If Little's Law is violated, it means that either the testing process or the test data captured is incorrect.
—The Art of Computer Systems Performance Analysis by Raj Jain
