Fig. 11.1.6 An I/O operation.There are two kinds of speeds found in a computer—electronic speeds and mechanical
speeds. Electronic speeds are measured typically in nanoseconds. Mechanical speeds are
measured in terms of milliseconds. The difference in speeds is akin to flying on a jet
airplane and riding a bicycle. There is that much difference between the two types of
speeds.
The internal operations of a computer operate in electronic speeds. The I/O operations of
reading or writing to the database operate at mechanical speeds.
In order to get a program to operate quickly, the analyst needs to minimize the number of
I/Os that are being done.
Minimizing the number of I/Os being done has the effect of speeding a program in its
execution. But minimizing I/Os also has the effect of reducing the speed of every other
transaction that is awaiting execution.
In a computer, a single program executes one at a time. The other programs that need to
execute wait while the one program that is in execution finishes. The time the other
programs have to wait is called “queue” time.
Fig. 11.1.7 illustrates queue time.
Chapter 11.1: Operational Analytics: Response Time