16.6 Maintenance

Maintenance is the introduction of relevant changescorrections or enhancementsto preserve the system's integrity. The starting point for maintenance is event registrations. On the basis of event registration, maintenance requirements must be put in order of priority, distinguishing between correcting errors and making desired improvements. They may also include requirements for adding facilities, such as new or more printers.

Maintenance of a product is generally regarded as a series of small projects in themselves , each running through the traditional development activitiesrequirement specification, design, coding, and testbut usually on a smaller scale than the original development.

New Versions

Each company must decide when and how to release new versions. In some companies, especially where the company itself is the customer, new versions are released on a running basis as event registrations are received and handled. Other companies gather event registrations and resulting change requests and release new versions at previously defined intervals, such as quarterly. It may be an advantage not to send out new releases too frequently, because of the learning curve for the users. Emergency situations may naturally arise.

Configuration Management Considerations

Configuration management during maintenance is fundamentally the same as during production. Identification of new configuration items must take place, both entirely new ones that are now needed (maybe in the form of a patch) and new versions of existing ones. New items must be placed in storage and released for usage. New events will be observed and must be handled. New status reports must be produced. And so on, until the product is no longer maintained . This may be more distant than the original developers think. How many developers who made software in the seventies and eighties imagined that their products would live to see the millennium ?

Example

A company had to make a small correction for the millennium in a system from 1985. They had access to the source code and even the original programmer, but the question was whether they would be able to create a new version. Would there be a compatible PC, the correct operating system, a suitable diskette driver, the correct compiler and run-time library, and so on? There was, but this was sheer luck.

In some cases, the only way to ensure that a product can be reproduced ten or more years later is to take a full development environment, with everything that belongs to it, and place it in a corner. This may be a waste of resourcesbut it may also be a company's sheet anchor. Moreover, one should check that the environment functions in isolation, so that it does not depend on, say, an Internet connection.