Ref: Connolly and Begg 6th ed., Chapter 10 Chapter Name September 98 CSD305 Advanced Databases Database Lifecycle and DBMS Selection CSD305 Advanced Databases Ref: Connolly and Begg 6th ed., Chapter 10 1

Lecture overview Database development lifecycle Database definition Requirements collection and analysis Database design DBMS selection Implementation Testing Maintenance Often many software projects are late, over budget, unreliable and difficult to maintain and perform poorly Known as the ‘software crisis’ or ‘software depression’ still an issue today 80-90% do not meet performance goals Around 80% delivered late and over budget Around 40% fail or abandoned Under 40% address training and skills requirements Less 25% properly integrate Just 10-20% meet all success criteria (OASIG,1996) Reasons: Lact of complete requirements spec Lack of appropriate development methodology Poor decomposition of design into manageable components. Solution More structured approach SDLC More correctly for DB DSDLC CSD305 Advanced Databases

Database system development lifecycle (DSDLC) Definition- scope and boundaries, major user views, its users and app areas Data conversion and loading- loading data from old to new and where poss converting any existing apps Operational maintenance – new system monitored and maintained. New requirements incorporated through the preceding stages of the lifecycle CSD305 Advanced Databases

Database Definition Specifying scope and boundaries of the database system and the major user views. User view defines what is required of a database application from perspective of: a particular job role (such as Manager or Supervisor) or enterprise application area (such as marketing, personnel, or stock control). CSD305 Advanced Databases

Requirements collection and analysis The process of collecting and analysing information about the part of the organization that is to be supported by the database system, and using this information to identify the requirements for the new system. a description of the data used; the details of how data is to be used; any additional requirements for the new database system. CSD305 Advanced Databases

Requirements collection and analysis Centralised approach Diagrams represents management of user views This approach preferred when significant overlap in requirements System not overly complex How to deal with multiple user views three approaches; The centralised approach The view integration approach A combination of both Centralised approach: Requirements for each view merged to a single set of requirements. A global data model representing all views created during database design Global data model composed of diagrams and documentation to describe the data requirements of users View integration approach Requirements for each user remain separate Local Data models created for each user Merged later during database design stage Used when significant difference between user needs Database sufficiently complex to divide work into manageable chunks CSD305 Advanced Databases

Database Design The process of creating a design that will support all major application areas and user groups any transactions required on the data performance requirements for the system Three phases of database design: Conceptual database design independent of all physical considerations Logical database design Based on data model but independent of DBMS and physical considerations (normalisation) Physical database design. Base relationships, file organisation and indexes Integrity constraints, security measures CSD305 Advanced Databases

Database Design CSD305 Advanced Databases

Database design – Criteria for an Optimal Data Model CSD305 Advanced Databases

DBMS Selection The selection of an appropriate DBMS to support the database system. Undertaken at any time prior to logical design provided sufficient information is available regarding system requirements. Performance, ease of restructuring, security and integrity constraints Main steps to selecting a DBMS: determine DBMS requirements shortlist two or three products; evaluate products; recommend selection and produce report. May be infrequent, enterprise needs expand, existing systems needs replacing Need to select a system that meets current and future requirements balanced against cost CSD305 Advanced Databases

Business requirements imply DBMS requirements strategic tactical resource constrained external factors innovation i.e. technology driven CSD305 Advanced Databases

DBMS shortlisting and evaluating Essential DBMS Requirements Essential DBMS requirements-define terms of reference Shortlist a few products CSD305 Advanced Databases Desirable requirements Evaluate shortlisted products

Essential requirements Cost Availability Vendor support Compatibility with existing hardware/software Political Existing users Online research https://www.infoworld.com/category/database/ For comprehensive reviews Essential requirements – define terms of reference. Includes objectives, scope of study and tasks that need to be undertaken Constraints and timescales for study. Description of criteria based on user requirements Preliminary list of possible products Shortlist 2 0r 3 products Can be done through contacting existing users (can provide specific details on vendor support, support for specific applications, whether HW platforms are more problematic than other Often benchmarks available to compare performance Infoworld online technology test centre www.infoworld/test-center.com for comprehensive reviews CSD305 Advanced Databases

DBMS Desirable Features For purpose of evaluations features can be assessed as groups (or individually) If features simply checked in regards how good/bad each is can be difficult to make comparisons So weight features and/or groups with respect to importance to organisation So obtain overall weighted value that can be used to compare CSD305 Advanced Databases

DBMS Desirable Features CSD305 Advanced Databases

Selecting a DBMS Product For each shortlisted DBMS; for each feature group --- Each selected feature given rating out of 10, weighting out of 1, to indicate its importance relative to other features in group Score = rate * weight e.g. Ease of reorganisation rated 4, weight of 0.25 = score 1.0 This feature highest weighting, indicating its importance in this group Weighted 5 times higher than data compression 0.05 Storage and memory requirements rating of 0 so not include in this evaluation. Next sum up all scores to produce total score. This is now group rating Group rating is subject to group weighting which indicates its importance relative to other groups Group score = grate*gweight CSD305 Advanced Databases

Selecting a DBMS Product Assemble a score for the DBMS Group Rating Weighting Score Data defn. 6.5 0.1 0.65 Physical defn. 5.75 0.25 1.44 Accessibility 6.00 0.60 Transaction handling 5.50 0.15 0.825 Utilities 3.25 0.2 Development 4.50 0.45 Other 5.00 0.50 This DBMS 5.115 Sum up all the scores, score for dbms. Highest scores best selection CSD305 Advanced Databases Do the same for the other shortlisted DBMSs; highest score wins

Implementation Build the database (and applications). Changeover Data conversion and loading May be possible to convert and use application programs from old system for use by new system. CSD305 Advanced Databases

Testing Database tested as part of application testing Verify database against the requirements e.g. response time, throughput (transactions/second) Verify non-functional requirements e.g. backup, security, response time, throughput (transactions/second) CSD305 Advanced Databases

Maintenance corrective, perfective, adaptive Process of monitoring and maintaining system following installation. Monitoring performance of system. if performance falls, may require tuning or reorganization of the database. Maintaining and upgrading database application (when required). Incorporating new requirements into database application. CSD305 Advanced Databases

Operational issues Process of operating the new system. Technical Interfacing to legacy systems Interfacing to external systems Human resources Right mix of people with right skills Training/career paths etc. Organisational Fault reporting/fixing procedures CSD305 Advanced Databases

Summary Database System Development Lifecycle (DSDLC) Selection of DBMS CSD305 Advanced Databases