Database Management Systems (DBMS): Implementation Approaches and Advantages, Diapositivas de Principios de la Gestión de Bases de Datos

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Databases

Part 4 - DBMSs

Comp. Sci. Preliminaries

Databases Lab

Contents and bibliography

Contents

4.1. Implementation approaches (Files vs. DBMS) 4.2. DBMS-based approach: advantages

Bibliography

• Elmasri, R.; Navathe, S. (2011). Database Systems. Addison-Wesley
• Date, C.J. (2001). Introducción a los Sistemas de Bases de Datos. Prentice Hall.
• Silberschatz, A.; Korth, H.; Sudarshan, S. (2011). Databases System Concepts. Mc Graw Hill.

Implementation approaches

• How do we implement and manipulate a relational database?
  • The relational model provides us with a way of organizing

data that is very simple to understand and manipulate.

• However, it is an abstract view, that we must implement in

some way.

• Options:
  • File-based approach
  • DBMS approach (Database Management System)

Implementation approaches: Files

• File-based approach:
  • Our applications manage all the information in files in a specific format (for instance, spreadsheets)
  • Applications directly manage the files.
  • Disadvantages:
    • We would have to program everything (complex)
    • Similar code in all the applications (repetitive)

Implementation approaches: Files

• Questions to answer:
  • How do I access the data in my files?
  • How do I add integrity controls for my information?
  • How do I allow multiple users to access data

simultaneously, while guaranteeing consistency?

• How do I guarantee data security?
• How do I manage error recovery?
  • Answer: I need to CODE it
• What happens if I change the properties of my files?
  • Answer: I need to (RE)CODE it

Implementation approaches: DBMS

• DBMS approach:
  • Set of programs that allow us to create and manipulate databases
  • Implements generic services that are needed in all the applications
  • Does most of the work for us and hides the low-level details
  • Can simultaneously manage multiple databases
  • Usually works in a dedicated server. It must be a device with enough resources (processor, memory, disk)

DBMS approach: advantages

• DBMS approach advantages :
  • Centralized data administration
  • Physical medium independency
  • Simplicity in data access
  • Integrity control
  • Concurrent access control
  • Security
  • Error recovery

DBMS approach: advantages

• Centralized data administration
  • All data are stored in a central server
  • One or more database administrators are in charge of managing the server - The administrator handles the server configuration: database definition; integrity rules; access and security policies; recovery mechanisms, etc.
  • Centralized management:
    • Is easier to handle: the job of the administrator is simpler
    • It is more reliable : only the administrator is authorized to change the server configuration
    • Avoids data isolation : information distributed across multiple computers, multiple files and multiple formats.

DBMS approach: advantages

• Centralized management: ALL data are in the DBMS, independently of how many programs access those data.
• Data organization is the same for ALL the programs.

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DBMS approach: advantages

• DBMS approach advantages :
  • Centralized data administration
  • Physical medium independency
  • Simplicity in data access
  • Integrity control
  • Concurrent access control
  • Security
  • Error recovery

DBMS approach: advantages

• DBMS approach advantages :
  • Centralized data administration
  • Physical medium independency
  • Simplicity in data access
  • Integrity control
  • Concurrent access control
  • Security
  • Error recovery

DBMS approach: advantages

• Integrity control
  • All our databases must fulfill the integrity constraints that have been identified.
  • Constraints are guaranteed by the applications by means of controls in the data input interfaces.
  • The DBMS is able to guarantee that certain integrity constraints are fulfilled. - Examples: - Domain constraint - Entity integrity constraint - Referential integrity constraint - Unique values - Mandatory (non-null) values
  • Objective:
    • Simplify controls in the applications
    • Minimize effects of errors in application code

DBMS approach: advantages

• Concurrent access control:
  • Inconsistencies are possible when several users concurrently access the same datum

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DBMS approach: advantages

• DBMS approach advantages :
  • Centralized data administration
  • Physical medium independency
  • Simplicity in data access
  • Integrity control
  • Concurrent access control
  • Security
  • Error recovery