Database System Environment

Introduction

• Topics covered: Database system environment details
• Focus on software components in DBMS

Component Modules in DBMS

1. Schemes Definition

   • Defined by Database Administrator (DBA) and designers using Data Definition Language (DDL)
   • DDL compiler processes schema definitions and stores them in the catalog
   • Catalog: Information about file size, data types, storage, constraints
   • Modules access the catalog as needed

2. Query Compiler

   • Handles high-level queries
   • Analyzes, interprets, and creates database access code
   • Calls runtime database processor for execution

3. Pre-Compiler

   • Extracts Data Manipulation Language (DML) commands from application programs
   • Programs usually in C, C++, Java, etc.
   • Extracted DML commands sent to DML compiler

4. DML Compiler

   • Compiles DML commands into object code for database access
   • Rest of the program sent to host language compiler
   • Compiled object code and rest of the program linked as compiled/canned transactions

5. Runtime Database Processor

   • Handles database access at runtime
   • Processes retrieval/update requests on stored database

6. Stored Data Manager

   • Controls disk access
   • Manages data transfer between disk and main memory
   • Allows other DBMS modules and application programs to process data in main memory

Database System Utilities

1. Loading Utility

   • Loads existing data files into the database
   • Reformats data automatically based on source and target file structure

2. Backup Utility

   • Creates backup copies of the database
   • Incremental backups: Records only changes since the last backup, saving space

3. File Reorganization Utility

   • Reorganizes database files to improve performance

4. Performance Monitoring Utility

   • Monitors database usage
   • Provides statistics for DBA to decide on reorganizing files

Other Tools

1. CASE Tools (Computer-Aided Software Engineering)

   • Used during the database design

2. Data Dictionary/Data Repository System

   • Stores catalog information
   • Stores descriptions of application programs, user info, etc.
   • Accessible by users and DBAs

3. Application Development Environments

   • Environment for developing database applications
   • Examples: JBuilder, PowerBuilder

4. Communication Software

   • Allows remote access to the database
   • Connections via phone lines, LAN, personal computers

Conclusion

• Covered: Component modules of DBMS, database system utilities, and different tools
• Key Takeaway: Understanding the database system environment and its components