What is the Goal of Performance Optimisation?

"So this is the goal: To make money by increasing net profit, while simultaneously increasing return on investment, and simultaneously increasing cash flow." 

"The Goal" by Eli Goldratt and Jeff Cox is all about performance, without being anything to do with computers.  
It is a story of a man who has to save his manufacturing plant from closure by making it profitable.  The language is about manufacturing, but it applies to any system of processes, including any software application and your Oracle (or any other) database!  
I was checking a quote from it, and I ended up reading it again.  It was 20 years since I first read it.  Then, it completely changed how I thought about performance.  It remains just as valid today.  
It is good to be reminded of these fundamental principles every now and then.
"There are three measurements which express the goal of making money ... throughput, inventory and operational expense"
"Throughput is the rate at which the system generates money through sales.
Inventory is all the money that the system has invested in purchasing things which it intends to sell.
Operational expense is all the money the system spends in order to turn inventory into throughput."
"A plant in which everyone is working all the time is very inefficient."
"A bottleneck is any resource whose capacity is equal to or less than the demand placed upon it.  And a non-bottleneck is any resource whose capacity is greater than the demand placed on it."
"What does lost time on a bottleneck mean?  It means you have lost throughput."
"The capacity of a plant is equal to the capacity of its bottlenecks."
"A system of local optimums is not an optimum system at all; it is a very inefficient system."
"An hour lost at a bottleneck is an hour lost for the entire system.
An hour saved at a non-bottleneck is worthless."
"1. IDENTIFY the system's constraint(s).
2. Decide how to EXPLOIT the system's constraint(s).
3. SUBORDINATE everything else to the above decision.
4. ELEVATE the system's constraint(s).
5. WARNING!!!! If in the previous steps, a constraint has been broken, go back to step 1, but do not allow INERTIA to cause a system's constraint."
"I started to have a very good guideline; if it comes from cost accounting it must be wrong."

Performance optimisation is sometimes viewed as a black art.  It is not.  Instead, like detection, it "is, or ought to be, an exact science, and should be treated in the same cold and unemotional manner".  

  • "The Goal" explains the general principles.