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Structure of dbms
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- 3. Architecture of DBMS A database system is divided into modules Each module provides set of responsibility for system Components of database system are Storage manager Query processor
- 4. Query Processor Itis one of the functional components of DBMS. The query processor receives as input queries in the form of SQL text and optimizes them, and completes their execution by employing specific data access methods and database operator implementations. Query Processor As query is very much necessary to find out only the data user need from tons of data of the database, query processor is very important to process these query requests.
- 5. Query Processor components DML Compiler – It processes the DML statements into low level instruction (machine language), so that they can be executed. DDL Interpreter – It processes the DDL statements into a set of table containing meta data (data about data). DML queries – Data manipulation language (DML) statements add, change, and delete Database table data Query Optimizer – It executes the instruction generated by DML Compiler. Query evaluation engine- which executes low-level instructions generated by the DML compiler.
- 6. Storage Manager Astorage manager is a program module which is responsible for storing, retrieving and updating data in the database. Storage Manager is a program that provides an interface between the data stored in the database and the queries received. It is also known as Database Control System. It maintains the consistency and integrity of the database by applying the constraints and executes the statements.
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- 8. Storage Manager Components AuthorizationManager – It ensures role-based access control, checks whether the particular person is privileged to perform the requested operation or not. Integrity Manager – It checks the integrity constraints when the database is modified. Transaction Manager – It controls concurrent access by performing the operations in a scheduled way that it receives the transaction. Thus, it ensures that the database remains in the consistent state before and after the execution of a transaction. File Manager – It manages the file space and the data structure used to represent information in the database. Buffer Manager – It is responsible for cache memory and the transfer of data between the secondary storage and main memory.
- 9. Data structure usedby dbms Data Files : It stores the database. Data Dictionary : is a collection of names, definitions, and attributes about data elements that are being used in a database. A Data Dictionary also provides metadata about data elements. Indices : Provide fast access to data items that hold particular values. Statistical Data : It stores statistical information about the data in the database.