Database Management System (DBMS)

• A software system designed to store, manage, and facilitate access to databases
• Typically used to refer to relational databases with transactions
• Many types: relational, key value, graph, matrix, etc.
• File system vs DBMS
  • File system runs on top of the operating system, while a DBMS has its own disk space and buffer management
  • DBMS has a declarative query system, file system has imperative direct access
  • DBMS has concurrent access and recovery
  • DBMS makes development easier because you can use the schema
• Advantages
  • Good data modeling
  • Simple, efficient, ad hoc queries
  • Data integrity and security
  • Data administration
• How
  • Data modeling (ER, Relational Model, FDs)
  • Query languages (Relational Algebra, SQL)
  • Views, indexes, constraints, triggers, UDFs

Relational DBMS Architecture

• Layered architecture
  • Query Optimization and Execution
  • Relational Operators
  • Files and Access Methods
  • Buffer Management
  • Disk Space Management
• Bottom 3 need concurrency control and recovery

Levels of Abstraction

• External schema (aka Views)
• Conceptual (logical) Schema
  • The table and relations
• Physical Schema
  • How the data is stored on a disk
  • Indexes