Spectrum of System Integrity

This is a schema for the various categories of systems integrity and potential system failures.

This schema is meant to:

help you recognise the various categories and likely types of failure for a system and/or project,
help you assessing their relevance,
prompt you to prepare a contingency plan in each relevant category.

Each category should be expanded into a plan in its own right e.g. Hardware Disaster Recovery Plan. Note that the contingencies offered are intended to match the examples; you need to examine and recognise your own most critical points of impact, and work out contingencies for each case.

Subject area	Class	Most likely point of impact	Example	Contingency
Purpose	Obsolescence	Changes in the business at the highest level	New legislation, Take over by another business	None? (go back and start again)
Scope of system	Requirements	Unexpected changes in requirements	Project expanded or reduced at short notice	Terms of reference to include renegociation with client/users
Environment	Locations	Building(s) not available	Fire, bomb scare, double booking	Alternate site(s)
	Personnel	Non availability	Off sick	Multi-skilled people. Role shadowing.
Conceptual and temporal	Conceptual design flaws,	Items missing from design	Backup of data	Design reviews
	Temporal constraints.	Time delays of other systems / projects	Data feed from other systems not ready on time	Build estimated &/or waiting time into project schedule
Financial	Budget costs, cuts, overruns	Block on further development	Exceeding agreed budget	Reserve funds. Barter with other projects.
Communications	Internal	Local area network	Cabling failure	Alternate data transfer e.g. USB drive, WiFi, etc.
	External	Wide area network	Telecommunications failure	Alternate comm's channels e.g. VPN, mobile data
Software	Internal	Failure to meet functional specification	Design failure, inadequate testing	Usability Clinics with clients, Unit and System Testing
	External	Inadequate performance	Too slow!	Benchmark and reliability guarantees from 3rd parties.
Hardware	Individual computers	Failure of critical components	Server failure	Server mirroring and replication
Other	Third parties	Supply of critical services	Electricity supply failure	UPS