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Object-Relational Data Model in Database

Object-Relational Data Model in Database

  •  Features of both Object oriented data model and Relational Data Model.
  •  Retain the core-relational foundation of the relational model :-  Declarative access to data
  •  Collection types and Object orientation

Object-Relational Data Model incorporate the features of the object oriented data model and relational data model. Object-Relational Data Model retain the core-relational foundation of the relational model -that is  the declarative access to data. It extend the relational data model by providing collection types and object orientation. Object orientation provides inheritance. Collection types include nested relations,sets,multisets and arrays. The object relational model allows attributes of a table to be collections.

Transaction Manger in Database

Transaction Manger in Database

Storage Manager and Query Processor are two functional components of a database system. Transaction manager is one of the integral parts of storage manager.

Transaction manager ensures that the database remains in a consistent state  and allowing concurrent transactions to proceed without conflicting

Data Abstraction in Database

Data Abstraction in Database

In an abstract data type(ADT) ,the properties are visible to the user ,but its implemetation details are hidden from the user.A major purpose of a database system is to provide the users with an abstract view of data and hide its internal complexities.To hide the complexity from users database apply the  following levels of abstraction.

  • Physical Level
  • Logical Level
  • View Level

Physical Level
Physical Level is the lowest level of abstraction and it defines the storage structure.The physical level describes complex low level data structures in detail.The database system hides many of the lowest level storage details from the database programmers. Database Administrators may be aware of certain details of physical organization of data.

Logical Level
This is the next higher level of abstraction which describe what data are stored in database, relation between data, types of data etc . Database programmers, DBA etc knows the logical structure of data

View Level
This the highest level of abstraction. It provides different view to different users. At the view level users see a set of application programs that hide details of data types. The details such as data type etc are not available at this level. Only view or Access is given to a part of data according to the users access right

Storage Manager in Database

Storage Manager in Database

 

The storage manager is important because database typically require a large amount of storage space.So it is very important  efficient  use of storage, and to minimize the  movement of data to and from disk .

A storage manager is a program module that provides the interface between the low-level data stored in the database and the application programs and the queries submitted to the system.

The Storage manager is responsible for the interaction with the file manager.

The Storage manager translates the various DML statements into low level file system commands.

Thus the storage manager is responsible for storing, retrieving, and updating data in the database.

The storage manager components include the following.

 
  • Authorization and Integrity Manager
  • Transaction Manger
  • File Manager
  • Buffer Manger

The storage manager implements the following data structures as part of the physical system implementation.Data File, Data Dictionary, Indices.Data files stores the database itself. The Data dictionary stores meta data about the structure of database, in particular the schema of the database. Indices provide fast access to data items.

 

 

 

 

Atomicity in Transactions in Database

Atomicity in Transactions in Database

Atomicity is one of the ACID properties of transaction. Atomicity property of  transaction ensures that all operations in the transaction must occur completely or none should occur. Recovery manager of the DBMS handles the atomicity property.