When designing applications, there are many ways to classify the requirements: Functional requirements, non-functional requirements, emerging requirements, system requirements, process requirements, constraints on the development and on the operation--to name a few.

Computer applications operate on data, which resides somewhere and which needs to be accessed from either a local or remote location. The applications manipulate the data, performing some kind of processing on it, and then present the results to whomever was asking for in the first place.

This simple description involves many processes and many operations that have many different requirements, from computers to software products.

Although each application design is a separate case and can have many unique requirements, some of these are common to all applications that are part of the same system. Not only because they are part of the same set of applications that comprise a given information system, but also because they are part of the same installation, which is connected to the same external systems.

One of the problems faced by systems as a whole is that components are spread across different machines, different platforms, and so forth, each one performing its work in a server farm environment.

An important advantage to the zSeries® approach is that applications can be maintained using tools that reside on the mainframe. Some of these mainframe tools make it possible to have different platforms sharing resources and data in a coordinated and secure way according to workload or priority.

The following is a list of the various types of requirements for an application. The list is not exclusive; some items already include others.

• Accessibility
• Recoverability
• Serviceability
• Availability
• Security
• Connectivity
• Performance objectives
• Resource management
• Usability
• Frequency of data backup
• Portability
• Web services
• Changeability
• Inter-communicable
• Failure prevention and fault analysis