System Maintenance: Most information systems required at least some modification after development. The need for modification arises from a failure to anticipate all requirements during system design and/or from changing organisational requirements. The changing organizational requirements continue to impact most information systems as long as they are in operation. Consequently periodic systems maintenance is required for most of the information systems. Systems maintenance involves adding new data elements, modifying reports, adding new reports, changing calculations, etc.
Maintenance can be categorised in the following two ways:
1. Scheduled maintenance is anticipated and can be planned for. For example, the implementation of a new inventory coding scheme can be planned in advance.
2. Rescue maintenance refers to previously undetected malfunctions that were not anticipated but require immediate solution. A system that is properly developed and tested should have few occasions of rescue maintenance.
One problem that occurs in systems development and maintenance is that as more and more systems are developed, a greater portion of systems analyst and programmer time is spent on maintenance. An information system may remain in as operational and maintenance mode for several years. The system should be evaluated periodically to ensure that it is operating properly and is still workable for the organization. When a system becomes obsolete, i.e., new opportunities in terms of new technology are available or it no longer satisfies the organization‘s needs, the information system may be replaced by a new one generated from a fresh system development process.