Database System Architecture
- 1. DATABASE SYSTEM ARCHITECTURE Prepared by, Mr. K.Vignesh Saravanan Assistant Professor Department of Computer Science and Engineering Ramco Institute of Technology Rajapalayam
- 2. Centralized DBMS – The application program + user interface + control of DBMS (data server) in a single machine – Access through the single machine – very slow computations, lack of concurrency
- 3. Two tier architecture – Client-server architecture – Client – machine used by end-user. – Server – high end machine holds software and hardware – The application programs run on the client side – Client will send Query / request transaction through ODBC / JDBC
- 4. Three tier architecture – Client machine just acts as a front end and does not contain any direct database calls – client end communicates with an application server – application server in turn communicates with a database system to access Data – applications that run on the World Wide Web
- 5. Database System Structure – Database Users and Administrators – Transaction Management – Data Storage Manager – Query Processor
- 6. Database Users and Administrator • Naive users are unsophisticated users • who interact with the system by invoking • one of the application programs • Application programmers are computer • Professionals who write application programs • Sophisticated users interact with the system • using tools such as data analysis software • Database Administrator(DBA) - Schema definition, modification, Grant/revoke access, Maintenance.
- 7. Storage Manager • Storage requires huge amount of data (largest database) • Interface between internal Disk and application program and queries submitted to the system • Responsible for storing, retrieving and updating data in the database • Authorization and integrity manager – checks integrity constraints and checks the authority of users to access data. • Transaction manager - ensures that the database remains in a consistent(correctness) all the times. • File manager - manages the allocation of space on disk storage and the data structures used to represent information stored on disk. • Memory(Buffer) manager - which is responsible for fetching data from disk storage into main memory, and deciding what data to cache in main memory.
- 8. Disk Storage • Storage manager interacts with several data structures at physical level (Disk storage) – Data files, which store the database itself. – Data dictionary, which stores metadata about the structure of the database. – Indices, which can provide fast access to data items. Like the index in this textbook, a database index provides pointers to those data items that hold a particular value.
- 9. Query Processor • The query processor components include: DDL interpreter - which interprets DDL statements and records the definitions in the data dictionary. DML compiler - which translates DML statements in a query language into an evaluation plan consisting of low-level instructions that the query evaluation engine understands. Query evaluation engine, which executes low-level instructions generated by the DML compiler.
- 10. Transaction Management • A transaction is a collection of operations that handles transaction in the database by ensuring the properties: • Atomicity - all-or-none • Consistency – correctness of data • Durability – persistence (data should be present) • Failure recovery – recover from system crash