System Fundamentals: Organizations, Changeover and System Design
What the exam tests
System fundamentals examines how an organization plans, installs, operates and changes an information system. Questions often ask you to choose a changeover method, justify a backup strategy, or explain why a legacy system creates migration risk. The syllabus also covers subsystems, human interaction, deployment and system design.
Core rules
- A system is a set of interrelated components working toward a goal; a subsystem is a component of a larger system. Systems take inputs, process them, produce outputs and use feedback.
- Changeover methods: direct (old stops, new starts), parallel (both run), phased (modules go live in stages), pilot (one site first). Direct is cheapest and riskiest; parallel is safest and most expensive.
- Backups: full copies everything; incremental copies changes since the last backup of any type; differential copies changes since the last full backup. Restore time differs because incremental needs the full plus every incremental.
- Data migration needs field mapping, cleaning, trial runs and reconciliation. Legacy systems may use incompatible formats or undocumented rules.
- Deployment includes installation, configuration, training, documentation and support; user acceptance testing checks fitness for purpose.
Worked example
A school replaces attendance records. Direct changeover on a Monday could lose a day's data if the new system fails; parallel running for two weeks doubles data entry but lets staff compare old and new totals; a pilot at one campus limits risk. Reasoning: use pilot first, then parallel for critical registration periods, with weekly full plus nightly incremental backups. Reconcile migrated records by checksum before go-live.
Traps
Mixing up incremental and differential backups; assuming parallel is cheapest; treating migration as a file copy; ignoring legacy data quality; thinking testing ends at deployment.