SYSTEMS EVALUATION AND

SELECTION

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Topic 13

SYSTEMS MAINTENANCE

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The new system is now in operation.No systems ever remain as originally designedWhy? - changes in management.

- changes in legislations/ standards.- changes in operation due to newproduct or working environment.

- simply an improvement.

Factors Reduce Maintenance Costs

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Consider maintenence aspects during detailed design.

Comprehensive documentations - installation guide.

Good structured analysis and design.Good documentation of system.Use higher level of computer language.

Factors Lead to High Maintenance Costs

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Systems professional, accountants left the entity.

New staff may not fully understand the system.

Minor changes made to system are not reflected in documentation.

Who Performs Systems Maintenance?

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Developed in-housesystem analyst; programmer.

Commercial softwaresoftware vendor.provide upgrade version.

Types of Maintenance

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CorrectiveAdaptivePerfective

Corrective Maintenance

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The elimination of errors and problems in the system.

How to minimise?better system analysis and design.

better initial testing.

Adaptive Maintenance

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The modification of software to fit changing situations.

How to minimise?build flexibility into the system.e.g. tax rate as parameter, not program code.

use DBMS as interface between program and database.

Perfective Maintenance

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The improvement made for software’s efficiency.

The modification made to fit precisely the needs of the users.

How to minimise?better system design.use prototypes.