Database Enviroment

Database Enviroment

1. ANSI-SPARC Architecture

   • External Level: The user's view of the DB
     • Conceptual Level: This level describes what data is stored and their relationships
       • Internal Level: The physical representation of how the data is stored

2. Data Independence

   • Logical: Refers to the immunity of the external schemas to change the conceptual schema
   • Pysical: Refers to the immunity of the conceptual chema to change internal schema

3. Database Languages

   • DDL = Data Definition Language
     • Allows to describe and name entities, attributes or relationships
   • DML: Data Manipulation Language
     • Provides a set of operations to support the basic data manipulation operations on the data held in DB
       • Non-Procedural: Allows user to state what data is needed rather that how is retrieved
       • Procedural: Allows the user to tell the system what data is needed and how retrieve it

4. Data Model: Collection of concepts for describe and manipulate relations between data

   • Relational data model
   • Network data model
   • Hierachical data model

5. DBMS Functions

   • Data sotrage, retieval and update
   • User's accessible catalog
   • Transaction Support
   • Concurrency control services
   • Recovery Services
   • Authorization Services
   • Support for data and comunication
     • Utility Services
   • Integrity Services
   • Services to promote data independence

6. TP Monitor: A program that controls data transfer between clients and servers in order to provide a consistent enviroment