Database Architecture and Management Systems

Database Architecture

The definition of an information system is the detailed description of the system architecture.

Internal Level

The lowest level of abstraction, defining how data is stored on hardware and accessed. Responsibilities of the Database Administrator (DBA) include managing:

• Block size
• Relative position of stored records
• Addressing methods
• Overflows
• Indexing
• Storage changes
• Compression techniques

Conceptual Level

The mid-level of abstraction, representing the organization's data. This level encompasses partial views of different users' requirements and potential uses. It provides a total organizational vision, including data definitions and relationships. DBA responsibilities include:

• Defining the data stored in the database:
  • Data name
  • Attributes
  • Relationships with other data
• Isolating data representation from the specific machine internally and user requirements externally.

External Level

The highest level of abstraction, presenting different partial views for various database users. It's essentially the accessible portion of the conceptual model. Users interact with this level, accessing only the necessary parts of the database.

Database Management Systems (DBMS)

Concept

A Database Management System (DBMS) is an application enabling users to define, create, maintain, and control access to a database.

The DBMS acts as the interface between users, application programs, and the database. Key services include:

• Database Definition: Using Data Definition Language (DDL) to define data structure, types, and constraints.
• Data Manipulation: Using Data Manipulation Language (DML) to insert, update, delete, and query data.

A DBMS facilitates handling large amounts of information, allowing for database implementation, access, and maintenance. All database operations are processed by the DBMS.

Activity: Research the 10 largest databases globally and their information volume. Create an Excel chart comparing these databases.

Components

A DBMS comprises several modules, each with a specific function, built upon the operating system's services.

Query Processor: Transforms user queries into low-level instructions for the database operator.

Database Manager: Ensures data privacy, security, integrity, concurrent access, and interaction with the operating system. It acts as the interface for application programs and user queries, examining external and conceptual schemas to determine required records. It then instructs the file manager to execute the request.

File Manager: Manages the disk files storing the database. It establishes and maintains the list of structures and indexes defined in the internal schema. It does not directly perform data input/output.