Lect 03 Database Architecture

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Database Management 2010 : 

Database Management 2010 Database ArchitectureLec-3 Prepared byBilal Khan 4/21/2011

Database Architecture : 

It is very important to understand the architecture of database very well because What are those different level where we see the data in a database In order to make proper use of data and to design the database properly. The schema in the architecture refers to permanent structure of the database or intention of database. Database Architecture

History of Database Architecture : 

In the beginning data processing with the file processing environment was developed. Drawback: realized when Applo Moon Landing Project generate the huge amount of data and no proper recourse was available to handle or process that data. Solution: 1st database system was implemented name IMS. History of Database Architecture

History of Database Architecture : 

IMS 1st database system. IMS was based on hierarchical data model. Hierarchical data model support one to many relationship between entities. Drawback: IMS is tree like structure database, so people start finding it hard to implement different applications in different situation. Solution: IDS database system was implemented History of Database Architecture

History of Database Architecture : 

IDS IDS database system was based on Network data model. IDS support many to many relationship. After that the efforts was made to standardized the architecture of database. History of Database Architecture

History of Database Architecture : 

CODASYL Conference of Data System and Language committee appointed DBTG to make effort to standardized the database architecture. In 1971, DBTG proposed Two Level Architecture. History of Database Architecture

History of Database Architecture : 

Two Level Architecture System View: Schema It represent the view of whole organization database structure. User View: Subschema It represent the view of different user group. DDL is used to define the schema and subschema. History of Database Architecture

History of Database Architecture : 

ANSI American National Standards Institute reject the recommendation of DBTG. ANSI organized committee SPARC (Standard Planning and Requirement Committee) to suggest the architecture. SPARC proposed Three Level Architecture History of Database Architecture

History of Database Architecture : 

Three Level Architecture This architecture proposed in 1975 Data item can be described at three distinct level External Level Conceptual Level Internal Level History of Database Architecture

Three Level Architecture : 

Three Schema Component …... Three Level Architecture

Three Level Architecture : 

Objective Separate users view from the physical representation. Why??? Same data is view by different users differently. Example Date of Birth of student is store in one format. One user group view the DOB in dd-mm-yyyy format, another user view month dd, yyyy and an other view in yyyy-mm-dd format. Different use of the same data Three Level Architecture

Three Level Architecture : 

Objective Three level architecture give you the environment or facilities that you can store a consolidated view of all different views. Change the format of the data Practically store Seen by the user groups. By splitting it into different level it become much more easier. Three Level Architecture

Three Level Architecture : 

Three Schema Component External View The user view of the database. The way each user group use the data In external level, different external views of database. User may have different view of same data. E.g. date, time, etc. External view are represented independently in the three level schema architectures. Three Level Architecture

Three Level Architecture : 

Three Schema Component External View External view contain virtual calculated data. The data that is not actually stored in the database but is created when needed. E.g. age. So derived or calculate data can be shown to users. Three Level Architecture

Three Level Architecture : 

Three Schema Component User View Logical description of some portion of database that is require by the users to perform some task. Database is access by the different user group and every user group access the data according to its requirements. Users concern only the required data and have no relation with other data. Three Level Architecture

Three Level Architecture : 

External View Three Level Architecture First User View Second User View

Three Level Architecture : 

External View Three Level Architecture

Three Level Architecture : 

Three Schema Component Conceptual Layer It contain Logical structure of the database Describe whole database Conceptual schema developed on the bases of all the external views. Only DBA can access and understand conceptual schema In Conceptual schema all entities, attributes and their relationship are represented . Three Level Architecture

Three Level Architecture : 

Three Schema Component Conceptual Layer To maintain the integrity of data, few checks are used on the data. Conceptual schema represent semantic information about data It is relatively constant and design according to the present as well as future needs of an organization. But very few chance to make changes. Have no storage consideration Three Level Architecture

Three Level Architecture : 

Three Level Architecture

Three Level Architecture : 

Three Schema Component Internal View How the data is actually represented? In Internal schema DBMS concerned with the storage space for data and indexes. Record description Data compression and data encryption techniques Data define by the conceptual schema is store and some data added by DBMS by internal schema. Three Level Architecture

Three Level Architecture : 

Three Schema Component Internal View In internal view, formatting of data, arrangement of data is the responsibility of DBMS. In Internal view, DBMS interact with the operating system. Below the internal view there is a physical level which is not included in three level architecture. Three Level Architecture

Three Level Architecture : 

Three Schema Component Internal View In internal view, records are prepare by DBMS according to the need of organization and then it is handed over to OS with the appropriate guidelines or directions. OS prepare the physical layer and then store that data in binary form. Three Level Architecture

Three Level Architecture : 

Three Schema Component …... Three Level Architecture

Three Level Architecture : 

Schemas Mapping Link between two level is establish by schema mapping. Data item or object of one level interlink with the object of other level is called schema mapping Why??? Three Level Architecture

Three Level Architecture : 

Schemas Mapping Two type of schema mapping Conceptual Internal Mapping External Conceptual Mapping Three Level Architecture

Three Level Architecture : 

Schemas Mapping External Conceptual Mapping Create link between external level and conceptual level. Specifies mapping between objects in the external view to those in the logical model. Three Level Architecture

Three Level Architecture : 

Schemas Mapping Conceptual Internal Mapping Specifies mapping between objects in the logical model to those in the physical data model. Three Level Architecture

Three Level Architecture : 

Three Schema Component …... Three Level Architecture -------------------------------------------------------------- -------------------------------------------------------------- -------------------------------------------------------------- Ex/Con Mapping Con/Int Mapping

Data Independence : 

Outcome of three level architecture is data independence. Change in lower level do not affect the upper level. Type of data Independence Logical Data Independence Physical data Independence Data Independence

Data Independence : 

Logical Data Independence Changes in conceptual model do not effect external view. Logical data independence is the Immunity/resistance of the external schema to changes in the conceptual schema. Example Adding new file Adding new fields Change the type of Attribute Delete the Attribute Data Independence

Data Independence : 

Physical Data Independence Changes in Internal model do not affect conceptual model. Physical data independence is the Immunity/resistance of the conceptual schema to changes in the Internal schema. Example Changing in file organization Index Implementation Data Independence

Three Level Architecture : 

Three Schema Component …... Three Level Architecture -------------------------------------------------------------- -------------------------------------------------------------- -------------------------------------------------------------- Ex/Con Mapping Con/Int Mapping Logical data Independence Physical data Independence

Slide 34: 

Have a Nice Day 4/21/2011

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