unit - 1 DATABASE SYSTEM ARCHITECTURE.pptx

Short notes for the students to go through

1. DATABASE SYSTEM ARCHITECTURE

2. Users are differentiated by the way they expect to interact with the system • Application programmers • Sophisticated users • Naïve users • Database Administrator • Specialized users etc,

3. Application programmers: Professionals who write application programs and using these application programs they interact with the database system Sophisticated users : These user interact with the database system without writing programs, But they submit queries to retrieve the information Specialized users: Who write specialized database applications to interact with the database system. Naïve users: Interacts with the database system by invoking some application programs that have been written previously by application programmers Eg : people accessing database over the web

4. QUERY PROCESSOR: The interactive query processor helps the database system to simplify and facilities access to data. Various functionalities are DDL Interpreter: This is basically a translator which interprets the DDL statements in data Dictionaries. DML Complier: It translates DML statements query language into an evaluation Plan. Query Evaluation Engine: It executes the low level instructions generated by the DML Compiler. An execution plan is a blueprint for evaluating a query. It is evaluated by query evaluation engine.

5. STORAGE MANAGER: Storage manager is a program module that provides the interface between the low-level data stored in the database and the application programs and queries submitted to the system. The storage manager is responsible to the following tasks: interaction with the file manager efficient storing, retrieving and updating of data The Storage Manager include these following components/modules Authorization Manager Transaction Manager File Manager Buffer Manager

6. Authorization Manager: Validates the users who want to access the data. Transaction Manager: Database remains constant when the system fails. File Manager: Manage allocation of space on disk storage and representation of the information on disk. Buffer Manager: It handle the size of the memory. It manages the fetching of data from dis storage into main memory. It also decides what data to cache in main memeory .

7. DISK STORAGE Data Files: Used for storing database. Data Dictionary: used to store metadata. Indices: To provide fast access to data items present in the database. Eg .,Index page of the book