Section 7: Introducing large scale systems Introducing Large Scale Systems
Scale Large scale systems will usually be mission critical – the organisation cannot function without them. They will often involve more than one site and make heavy demands on infrastructure such as offices, equipment and networks. There will usually be a need for a large number of staff to be trained. The introduction must be planned in such a way that the organisation can continue to function during the changeover period.
Scalability Solutions based on generic software may not be feasible for large scale systems. A database may work perfectly well with a few thousand records on a single server, but not with several million records across multiple sites on a wide area network. Scalability may be difficult to test in practice and may need a simulated environment.
Testing Thorough testing before the system goes live should keep problems to a minimum.
Methods of introducing systems Direct Changeover The existing system is stopped and the new one simply replaces it. Quickest method, but highest risk. Stressful, because old system is unavailable if problems arise. System is down while data is transferred. Training is difficult.
Methods of introducing systems Phased Changeover System is brought in in stages, each stage replacing that stage in the old system. Slower than direct changeover but less risky. Each phase can be evaluated before moving on. Hard to evaluate complete system until the end. New system must be able to work with existing one.
Methods of introducing systems Pilot changeover The system is introduced on a limited scale, perhaps in a single branch The system is then rolled out to the rest of the organisation Good opportunity to test under real conditions Pilot system is available for training Pilot may not find problems due to load on full system Slower than direct changeover
Methods of introducing systems Parallel running Old and new systems run side by side for a limited period Safest method as both systems are available Training is easier, but staff may become confused by using both systems Very expensive and heavy load on staff and infrastructure New system must be able to work with existing one
Hardware installation May include: workstations plus peripherals such as printers server (s), backup devices and uninterruptible power supplies network cabling or wireless access points routers and switches. The infrastructure must be designed to give all users access to the correct data at acceptable speeds and protect them as far as possible from data loss.
Software installation May include: applications software, loaded on workstations or server network and client operating systems backup software. The network operating system controls and monitors security and must be configured to allow users correct levels of access. Accounting can be set up to monitor or charge for system resources.
Bookshop • Imagine a small bookshop selling new and second hand books in a town popular with tourists. • How will its ICT requirements differ from those of a national chain of bookshops? • Think about: • hardware • software • people • procedures