Time between failures and accessibility

Reliability and maintainability are factors of service availability defined in terms of faults and failures of one or more of the underlying service assets. However, what matters to user s is whether they can utilize the service or not. MTBF and MTRS mean little to them unless service level s are degraded or disrupted. The availability of services can be low even when service assets have high MTBF and low MTRS. In the time between failures, users expect the service to be easily accessible for utilization without inconvenience and undue effort on their part. Accessibility of a service is illustrated by the following examples.

An airline decides to improve customer satisfaction by increasing the number of ways for customers to purchase tickets and prepare for travel. It offers an online channel for passengers to check flight status, select seats, check in and print boarding passes before arriving at the airport. It also installs a network of self-service terminals that allow passengers with only carry-on baggage to proceed to the gates without having to wait in line at the counters. The net effect is that of virtually extending the ‘surface area’ of the airport check-in counter to locations convenient to the passenger, such as homes, offices and hotel rooms. The airline staff and other passengers at the airport benefit from reduced congestion. Passengers self-select between airport counters, self-service kiosks and the website channels, based on personal preference. They also respond to incentives offered by the airline to control the arrival of demand at particular locations. Similarly, a retail bank decides to make frequently requested and simple transaction s available on its website and wireless devices such as telephones and personal digital assistants (PDAs).

Both businesses have effectively increased the probability that their services will be easily available for use by their customers. The improvements are not through the MTBF and MTRS factors. The primary factor has accessibility through a wider area of contact between customers and service assets through well-defined interfaces (Figure 7.21). Increasing the ‘surface area’ of contact of the service delivery system directly results in increased service availability from the users’ perspective.

Figure 7.21 Increasing accessibility through multiple service channels

The following approaches increase the accessibility of services (Figure 7.22):

• Diversity of channels – provide multiple types of access channels so that demand goes through different channels and is safe from a single cause of failure. This is active diverse redundancy, which also provides utility to customers through preferred choices.
• Density of network – add additional service access points, nodes, or terminals of the same type to increase the capacity of the network with density of coverage. This is active homogeneous redundancy, which does not reduce vulnerability to a single cause of failure but reduces the complexity and provides economy of scale.
• Loose coupling – design interfaces based on public infrastructure, open source technologies and ubiquitous access points such as mobile phones and browsers so that the marginal cost of adding a user is low. It enables users to access the service from a wider range of locations and situations and also reduces the overall cost of maintaining a service. Advances in information security make this possible.

Figure 7.22 Channel capacity used for redundancy

Дата добавления: 2015-11-14