1. 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

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. Database Design
CSD305 Advanced Databases

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

10. 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

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

12. 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

13. Essential requirements
Cost
Availability
Vendor support
Compatibility with existing hardware/software
Political
Existing users
Online research
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 for comprehensive reviews
CSD305 Advanced Databases

14. 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

15. DBMS Desirable Features
CSD305 Advanced Databases

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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

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