Chapter 12
CHAPTER 12: SYSTEMS MAINTENANCE
1. Programming
It is a process of writing instructions for the computer execution and testing the written code to ensure it performs according to specification.
2. Objective Of Programming
To produce reliable software based on appropriate design specifications.
3. Purpose Structured Programming
To produce programs that have a definite form and are therefore more easily understood by the programmer and by anyone else who needs to read and understand them.
4. General Principles of Testing
· Prepare a test to specify the sequence in which the modules will be coded, individually tested and then integrated into the program
· Prepare test cases as part of the plan.
· Study and record all test results.
· Prepare test cases for both valid and invalid input condition.
· Do testing throughout the systems development phase not just at the end.
5. Types of Testing(UISV)
i. Unit Testing
Each program module is tested independently with predesigned test cases
ii. Integration Testing
One unit is added at a time to the structure and the resulting partial product is tested.
iii. System Testing
Test all related programs as a group.
iv. Volume Testing
Estimating the maximum load the system is expected to handle without major problems.
6. Systems Implementation
- Objective: To convert the existing system to the new system.
- Coverage:
i. Selecting and training system users
ii. Site preparation and installing new computer equipment
iii. File conversion
iv. Systems conversion
7. Problems Of File Conversion
i. Compatibility which may extend to matters such as different coding that the systems used, different formats or even different field sizes.
ii. Space Shortage to accommodate the combined data.
iii. Ensure that data are secured after data has been merged.
8. Types Of Cutover Methods
i. Parallel Cutover
- Most conservative
- Involves running the new system in parallel with the old system until all users are satisfied
- Results of operations based on the two systems are compared.
ii. Direct Cutover
- Use of the old system will be terminated as soon as the new system is brought into operation
- Incurs the greatest risks but minimizes the cutover costs if the new system performs to specifications
- Inexpensive
- Allowing possible major problems that can impair actual operations of the company
iii. Phased Cutover
- New system implemented by pieces or modules
- By modules it reduce the risk of system failure
- Can create incompatibilities new subsystems and yet-to-be replaced old subsystem
- It also can extend implementation of the new system for too long to be practical
9. Selecting The Appropriate Conversion Strategy
Cutover Method | Risk | Cost | Time |
Direct | High | Low | Short |
Parallel | Low | High | Long |
Phased | Medium | Medium | Medium |
10. Post Implementation Review
- Purpose: Post implementation review is to assess the quality of the newly implemented system.
- Post implementation review includes:
i. Accuracy, completeness and timeliness of output
ii. Quality and completeness of all documentation
iii. User satisfaction
iv. Adequate systems control and security measures
v. Hardware and software efficiency
vi. Accuracy of cost, benefits and time estimate
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