System analysis slides

Segment 7

2005 by Prentice Hall16-*

Learning ObjectivesExplain and contrast four types of system maintenance.Describe factors affecting maintenance costs.Describe maintenance management issues, including organizational structure, quality measurement, change management, and configuration management.Explain the role of CASE tools for system maintenance.



The Process of Maintaining Information SystemsProcess of returning to the beginning of the SDLC and repeating development steps focusing on system change until the change is implementedMaintenance is the longest phase in the SDLCFour major activities:Obtaining maintenance requestsTransforming requests into changesDesigning changesImplementing changes


Maintenance is like a mini-SDLC


The Process of Maintaining Information SystemsDeliverables and OutcomesSince the maintenance phase of the SDLC is basically a subset of the activities of the entire development process, the deliverables and outcomes from maintenance process are:Development of a new version of the software and new versions of all design documents created or modified during the maintenance effort


Types of System MaintenanceCorrective maintenanceChanges made to a system to repair flaws in its design, coding, or implementationAdaptive maintenanceChanges made to a system to evolve its functionality to changing business needs or technologiesPerfective maintenanceChanges made to a system to add new features or to improve performancePreventive maintenanceChanges made to a system to avoid possible future problems


By far, most maintenance is corrective, and therefore urgent and non-value adding.


The Cost of MaintenanceMany organizations allocate eighty percent of information systems budget to maintenanceWhat are the factors influencing the maintainability of systems?Maintainability is the ease with which software can be understood, corrected, adapted and enhanced.


Factors that influence system maintainability1. Latent defects -- The number of unknown errors existing in the system after installation.2. Number of customers for a given system -- Higher cost for higher number of customers/users. 3. Quality of system documentation -- quality of technical system documentation including test cases.4. Maintenance personnel -- Number and quality of personnel dedicated to the support and maintenance of the system


Factors that influence system maintainability (Contd)5.Tools -- Software development tools, debuggers, hardware and other resources. Tools such as those that can automatically produce system documentation where none exists can also lower maintenance costs.6.Sotware structure : Structure and maintainability of the software. Well-structured programs make it much easier to understand and fix programs.


A well-documented system is easier to understand, and therefore easier to maintain.


Conducting System MaintenanceManaging MaintenanceNumber of people working in maintenance has surpassed number working in development.Three possible organizational structures:SeparateMaintenance group consists of different personnel than development group.CombinedDevelopers also maintain systems.FunctionalMaintenance personnel work within the functional business unit.


Advantages and Disadvantages

Maintenance Organization TypeAdvantagesDisadvantagesSeparateImproved system and documentation qualityIgnorance of critical undocumented informationCombinedMaintenance group knows all about systemLess emphasis on good documentationFunctionalPersonnel have vested interestLimited job mobility and human or technical resources


Assignment of Maintenance PersonnelMaintenance work is often viewed negatively by IS personnel.Organizations have historically have rewarded people involved in new development better than maintenance personnel.Organizations often rotate personnel in and out of maintenance roles in order to lessen negative feelings about maintenance.


Conducting System MaintenanceMeasures of EffectivenessImportant factors to considerNumber of failuresTime between each failureType of failureMean time between failures (MTBF)A measurement of error occurrences that can be tracked over time to indicate the quality of a system


Expect lots of failures early, but as corrective maintenance takes place, error rate should decrease rapidly


Controlling Maintenance RequestsBased on the type of request, some method of prioritizing requests must be determined.Possible types of request:1.Error ( i.e a corrective maintenance request)2.Adaptation ( i.e request is to adapt the system to technology or business change)3.Enhancement (i.e request is to enhance the system so that it will provide new business functionality)Prioritizing scheme: Figure 16.8 shows a flowchart for controlling maintenance requests


Maintenance requests can be frequentPrioritize based on type and urgency of requestControlling Maintenance Requests


Evaluations are based on feasibility analysisThe Flow of a Maintenance Request


Configuration ManagementThe process of assuring that only authorized changes are made to the systemBaseline modulesSoftware modules that have been tested, documented, and approved to be included in the most recently created version of a system. A system librarian controls the baseline source code modules.System librarianA person responsible for controlling the checking out and checking in of baseline modules when a system is being developed or maintained


Configuration Management (Contd)It is the responsibility of the system librarian to keep copies of all prior versions of all system modules including the build routines needed to construct any version of the system that ever existed. It may be important to build old versions of the system if new ones fail, or to support users that cannot run newer versions on their computer system.Build routinesGuidelines that list the instructions to construct an executable system from the baseline source code


Configuration Management ToolsSpecial software systems for managing system configurationControls access to modules in the system libraryTwo typesRevision control: modules labeled as frozen (unchangeable) or floating (checked out by programmer for modification)Source code control: extend revision control to all interrelated modulesHistorical changes can be traced and previous versions can be reconstructed


Role of CASE and Automated Development Tools in MaintenanceTraditional systems developmentEmphasis on coding and testing.Changes are implemented by coding and testing first.Documentation is done after maintenance is performed.Keeping documentation current is often neglected due to time-consuming nature of task.

Development with CASEEmphasis is on design documents.Changes are implemented in design documents. Code is regenerated using code generators.Documentation is updated during maintenance.


Website MaintenanceSpecial considerations24 X 7 X 365 (?)Nature of continuous availability makes maintenance challengingPages under maintenance can be lockedDate and time stamps may be included to indicate the most recent changes.Check for broken linksHTML ValidationNew Pages should be processed by a code validation routine before publication.


Website MaintenanceSpecial considerations (continued)Re-registrationWhen content significantly changes, site may need to be re-registered with search enginesFuture EditionsConsistency is important to usersPost indications of future changes to the siteBatch changes to reduce the frequency of site changes.


SummaryIn this chapter you learned how to:Explain and contrast four types of system maintenance.Describe factors affecting maintenance costs.Describe maintenance management issues, including organizational structure, quality measurement, change management, and configuration management.Explain the role of CASE tools for system maintenance.

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System analysis slides