Physical System Database
The fundamental unit of data storage in Window Operating System is called Page. Each Page Size is 8 KB means 128 Pages can store in 1 MB. Every Page defined with Page Header and Page Body. 96 Bytes are allocated to Page Header that used to define Data File Information. 8096 Bytes are allocated to Page Body that used to store Raw Data.
Data Page can be categories into Data Pages and Index Data Pages. Data Pages contain Data in the form of Rows except Text, Image and Multimedia Files. Text, Image and Multimedia Files are stores separately from Data Pages and mapped with Pointer. Index Data Pages contain Index Key and Pointer that helps to map with Data Page.
When create Database, Window Operating System create Primary, Secondary, Log Data Files through Operating System that mapped with Database. Primary Data File is used to track and maintain Data Files. Secondary Data File is used to defragmentation and distribute Primary Data File work load and Maintain Data Files. Secondary Data File is an Optional Data File.
Log Data File is used to maintain Database Operation and Transaction Information that helps to recover Data, when failure Database Operation and Transaction. Statistical Data is stores in the Physical Database that information is helps to optimize Query Processing in the SQL Query Engine. Physical System Database is a combination of Metadata Database, Data Dictionary, Statistical Data and User Defined Database.
Metadata can define like "Data about Data". Metadata can categories into Technical Metadata and Business Metadata. Technical Metadata is helps to define RDBMS Operation and Business Metadata is helps to define Business Information Operation that deploy in the RDBMS Storage Disk and maintain by File Manager.
The compiled form of the Metadata Database Structure is called System Catalog. System Catalog is stores collection of Database Structure along with Metadata Database. Schema is helps to define particular Database Structure from System Catalog.
Schema can be define with collection of Table, Column, Data Integrity Constraint, View, Index, Stored Procedure, Function, Trigger, Package, Type, Sequence, Synonyms and other Database Elements that deploy in the RDBMS Storage Disk and maintain by File Manager.
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