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9.4 Legacy system management 255

Factor Questions

Supplier stability Is the supplier still in existence? Is the supplier financially stable and likely to
continue in existence? If the supplier is no longer in business, does someone else
maintain the systems?
Failure rate Does the hardware have a high rate of reported failures? Does the support
software crash and force system restarts?

Age How old is the hardware and software? The older the hardware and support software,
the more obsolete it will be. It may still function correctly but there could be significant
economic and business benefits to moving to a more modern system.

Performance Is the performance of the system adequate? Do performance problems have a
significant effect on system users?

Support requirements What local support is required by the hardware and software? If there are high
costs associated with this support, it may be worth considering system
replacement.
Maintenance costs What are the costs of hardware maintenance and support software licences? Older
hardware may have higher maintenance costs than modern systems. Support
software may have high annual licensing costs.
Interoperability Are there problems interfacing the system to other systems? Can compilers, for
example, be used with current versions of the operating system? Is hardware
emulation required?

because they feel that their supplier is aware of their needs. The outputs from such a
Figure 9.14 Factors
used in environment system are very important to the business and this system therefore has a high
assessment business value.
To assess a software system from a technical perspective, you need to consider
both the application system itself and the environment in which the system operates.
The environment includes the hardware and all associated support software (compil-
ers, development environments, etc.) that are required to maintain the system. The
environment is important because many system changes result from changes to the
environment, such as upgrades to the hardware or operating system.
If possible, in the process of environmental assessment, you should make meas-
urements of the system and its maintenance processes. Examples of data that may be
useful include the costs of maintaining the system hardware and support software,
the number of hardware faults that occur over some time period and the frequency of
patches and fixes applied to the system support software.
Factors that you should consider during the environment assessment are shown in
Figure 9.14. Notice that these are not all technical characteristics of the environment.
You also have to consider the reliability of the suppliers of the hardware and support
software. If these suppliers are no longer in business, there may not be support for
their systems.
To assess the technical quality of an application system, you have to assess a
range of factors (Figure 9.15) that are primarily related to the system dependability,