System Analyses Flashcards
Methods of Investigation
Study the existing system documentation
- Benefits
- Analyst can see how current system
‘should’ be operating
- Inexpensive method of gathering lots of
information fairly quickly
- Can identify storage requirements
- Drawbacks
- Staff may not be following procedures
in documentation and may be using
system in their own way
- Documentation may be out of date and
not updated to reflect system changes
Carry out a questionnaire of staff
- Benefits
- Relatively cheap to produce for a large
number of people
- Can be distributed worldwide
- Could be completed on-line so results
can be available very quickly
- Have to be designed by experts or
information could be unusable
- People are ‘too busy’ and may not
complete
- People may not give correct answers
Interview staff
- Benefits
- Can gather large amount of detailed
information
- Can make judgements on validity of
information from personal contact or
body language
- Can ask ‘follow up’ or ‘open ended’
questions to gather more detailed
information in selected areas
- Drawbacks
- Time consuming and expensive to carry
out
- Has to be carried out by trained
interviewer or closed questions written
by experts
- Difficult to analyse large amount of
information
- Difficult to analyse wide variety of
information
Observe the current system in practice
- Benefits
- Can actually see what is really
happening and do not have to rely on
what people tell you what they think is
happening
- Drawbacks
- Very time consuming and therefore
expensive to carry out
- Staff may feel like they are being
watched and therefore behave
differently so do not actually see what
goes on every day
- Cost of sending analysts around the
world.
Effects on the nature of employment
- New jobs have been created.
- Computers speed up the repetitive, boring
parts of jobs, leaving people free to do the
creative, interesting parts.
- Computers are cheaper to run, so have led
to a reduction in the cost of manufactured
goods. Repetitive jobs, such as copying
documents or stamping metal, are carried
out more reliably by computers.
- Some jobs have disappeared completely.
- People worry about not being able to use
new systems. - Learning new systems can take time.
- New computer systems can be expensive
to install. - Teleworking / video conferencing
Methods of Changeover
Direct “big bang” approach can be adopted - sudden change to new system
- Could be used where a failure would not be catastrophic
- Can be cheaper to implement
- New system is available immediately if required
- Can be the least disruptive if implemented well
- New system may not work as well until Marble Garden staff are fully used to using it
- If new system fails Marble Garden have no system which could be costly
Parallel running - both systems running together for a time
- Safest option as if new system fails they still have existing system
- New system is available immediately if required
- The outputs from the old and new systems can be compared to check that the new system is running correctly
- Expensive as require temporary staff or overtime for current staff to operate both systems
- Could cause confusion for staff / customers having two systems
Phased changeover - part-by-part (by functionality)
- Allows users to gradually get used to the new system
- Staff training can be done in stages
- All staff can focus on one area to resolve any problems
- Problems can be fixed quicker as more experts to resolve one functionality problem at a time
- Difficulties identified in one area can be resolved and managed in next area
- Might cause problems in the changeover period when they need to communicate with each other and have different systems
- Slower to get new system up and running compared to some other methods
- If a part of the new system fails, there is no back-up system, so data can be lost
Pilot changeover - part-by-part (by part of the organizational units within Marble Garden)
- All features of the new system can be fully trialled
- If something goes wrong with the new system, only a small part of the organisational operations of Marble Garden is affected
- The staff who were part of the pilot scheme can help train other staff.
- All staff can focus on one area to resolve any problems
- Difficulties identified in one area can be resolved and managed in next area
- For the office / department doing the pilot, there is no back-up system if things go wrong
- Might cause problems in the changeover period when they need to communicate with each other and have different systems
- Slower to get new system up and running compared to some other methods
Contents of System Documentation
- Any form of diagrams used in analysis and design.
- Descriptions of procedures and subroutines used.
- The data structure:
- What data structures have been used, database table designs and any other information about what data needs to be stored.
- Algorithm designs:
- Algorithms will normally be presented in pseudocode or flowchart form
- Annotated code listings:
- Code listings that abide by the coding standards set out by the development company. Normally self-documenting and/or annotated.
- Variable lists:
- Lists of the key variables listing their data types and purpose. More temporary variables, such as loop counters, would not be included.
- Data dictionary:
- This will describe all of the fields that need to be stored in the data structure including data type, size, relationship with other tables and a description.
- Design documents:
- Any relevant documentation from design phase.
- Hardware and software requirements.
- Performance
- Storage
- Networking
- Compatibility
- Operating system
- Configuration guide and options:
- How the system can be configured, which could be through a menu system or by editing configuration files.
- User Documentation:
- how software is to be installed and used
Data Backup
Types of backup routines:
- A generation file backup system
- This involves storage of three of the most recent versions of master file.(grandfather – father -son)
- Useful if one version is corrupted: the previous version(s) is still available.
- Data should be stored off site in case of a disaster.
- Incremental backup
- Only backs up data that has changed and writes over older back ups
- Useful as it saves storage space and is faster than full backup
- Only allows the user to restore the most recent backup.
Recovery routines:
- Buying new hardware
- Recovery after disaster – restoring databases/files General backup procedures
- Test if backups work/can be restored
- Frequency of backup
- Timing, e.g. overnight
- Staff member with responsibility for ensures suitable back-up
External hard disc drive
- Speed of access – Very fast transfer which is important as daily updates
- Cost per unit of storage – external hard disc is quite cheap per byte of storage
- Portability reason – external hard disc is physically quite small and can be easily stored securely and safely for example in a fire proof safe
- Suitability: Not suitable unless justified
Cloud storage / upload to a third party storage provider
- Speed of access – very fast transfer achievable (depending on network speed) for daily updates
- Cost per unit of storage – could be cheaper or more expensive than external disk – accept either with justification
- Data is stored securely and safely on protected servers (or should be!)
- Suitability: Suitable for a large company if justified (i.e. contract in place for location of storage etc)
Flash memory stick:
- Speed of access – Very fast transfer which is important as daily updates
- Cost per unit of storage – pen drive is quite cheap
- Portability reason – pen drive is physically small and can be easily stored securely and safely for example in a fire proof safe
- Suitability: Not Suitable for a large company
Magnetic tape
- Speed of access reason – Access to tape is serial and can be slow but could only back up files amended that day
- Cost per unit of storage reason – Tape is relatively (but drive can be expensive!) cheap compared with other secondary storage mediums
- Portability reason – Tape is physically small and can be easily stored securely and safely for example in a
fire proof safe.
- Suitability: Used widely by large companies historically
Testing
Alpha testing would sensibly be carried carry out by testers or developers within the developer’s own company
Beta testing would sensibly be carried carry out by a number of (privileged or existing) customers in exchange for their constructive comments
Acceptance testing would sensibly be carried carry out by a the prospective customer
Maintenance
An example of corrective maintenance is when a bug is found like an incorrect
calculation and the program is corrected, and the calculation changed to produce the correct result
An example of adaptive maintenance is when the program has to be altered to run on a different operating system like when a desk top application running on Windows has to be adapted to run on a mobile device / change in law for example change in rate of VAT
An example of perfective maintenance is when the program’s performance is improved like when a search algorithm is amended to produce results quicker
Feasibility
Feasibility - examine existing system to determine whether or not it is worth replacing with a new system
T - Technically feasible
E - Economically feasible
L - Legislation (law)
O - Organisationally feasible
S - Schedule (time)
