A less-demanding business, such as catalog sales, might lose only thousands of dollars
an hour by using a less-efficient manual system that acts as a stopgap measure.
But, regardless of the cost of lost business opportunity, an unexpected loss of availability
can cut into the productivity of employees and IT staff alike.
Table 11-1. System availability
% availability System downtime per year
Days Hours Minutes
95.000 18 6 0
96.000 14 14 24
97.000 10 23 48
98.000 7 7 12
99.000 3 16 36
99.500 1 20 48
99.900 0 9 46
99.990 0 1 53
99.999 0 0 5
256 | Chapter 11: Oracle and High Availability
Causes of Unplanned Downtime
There are many different causes of unplanned downtime. You can prevent some very
easily, while others require significant investments in site infrastructure, telecommunications,
hardware, software, and skilled employees. Figure 11-1 summarizes some
of the more common causes of system failures.
When creating a plan to guarantee the availability of your application, you should
consider all of the items shown in this chart as well as other potential causes of system
interruption that are specific to your own circumstances.
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