Posted by: ahmedashfaque | April 12, 2014

testing & quality assurance: preventive vs. reactive

In manufacturing world, we have 2 types of maintenance viz. preventive maintenance and reactive maintenance. In preventive maintenance, regular inspection of machines are done and if any machine found to be not performing well then before it breaks down, a shutdown is taken and machine is fixed before it breaks down. In reactive maintenance, when a breakdown occurs then a shutdown is taken and the machine is fixed.

When any breakdown of a machine occurs then a shutdown can not be taken immediately. For example, the breakdown occurs in the night shift and no adequate maintenance personnel are available to take a shutdown and fix it. Similarly, even in day time, it may take time to bring men and tackles at the breakdown site, do some preparation and then actually start working on the fixing work. Sometime, the preparation time could be as high as 10 hours. Thus there will be production loss for these 10 hours + actual time taken in fixing work.

On the other hand, if preventive maintenance is done then these preparation hours are saved. Already the maintenance team has information about what is to be fixed and they do the preparation work when the machine is running. Only when they are ready, the machine is stopped and then it is fixed.

One more advantage of preventive maintenance is that, if any problem is found with the machine (even though the machine is running but there is some noise or wear observed) it is fixed immediately. this results in saving major breakdown.

These concepts are analogous to what we see in the software development world. When the software product is being designed or constructed and any fault is found then it should be fixed immediately. If this fault is not detected and corrected then this will result in major (or a number of defects) later.

Inspection of source code during construction is analogous to preventive maintenance and doing testing after construction is analogous to reactive maintenance.



  1. very good insight. I am having some experience in plant maintenance and can relate to what you are talking about.

  2. Rather interesting. Good comparison of software processes with manufacturing processes.

  3. Reblogged this on Ashfaque Ahmed's Blog.

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