Introduction Set 2 Flashcards
What is DBMS Tier 3 architecture ?
It divides the complete system into three inter-related but independent modules.
What is the diagram for tier 3 dbms architecture?
https://www.geeksforgeeks.org/introduction-of-3-tier-architecture-in-dbms-set-2/
What level are there ?
Physical, Conceptual, External
What does the Physical level do?
The information about the location of database objects in the data store is kept. The physical level of a database describes how the data is being stored in secondary storage devices like disks and tapes and also gives insights on additional storage details
What does the Conceptual level do?
Data is represented in the form of various database tables. For Example, STUDENT database may contain STUDENT and COURSE tables which will be visible to users but users are unaware of their storage. Also referred as logical schema, it describes what kind of data is to be stored in the database.
What does the External level do?
Specifies a view of the data in terms of conceptual level tables. Each external level view is used to cater to the needs of a particular category of users. For Example, FACULTY of a university is interested in looking course details of students, STUDENTS are interested in looking at all details related to academics, accounts, courses and hostel details as well. So, different views can be generated for different users. The main focus of external level is data abstraction.
What is data independence?
A change of data at one level should not affect another level.
What are the two types of data independence?
Physical and Conceptual
Explain Physical Data Independence.
Any change in the physical location of tables and indexes should not affect the conceptual level or external view of data. This data independence is easy to achieve and implemented by most of the DBMS.
Explain Conceptual Data Independence.
The data at conceptual level schema and external level schema must be independent. This means a change in conceptual schema should not affect external schema. e.g.; Adding or deleting attributes of a table should not affect the user’s view of the table. But this type of independence is difficult to achieve as compared to physical data independence because the changes in conceptual schema are reflected in the user’s view.
What are the phases of Database Design?
Requirements , Conceptual Design , Logical Design, Physical Design
Explain Conceptual Design Phase
The requirements of database are captured using high level conceptual data model. For Example, the ER model is used for the conceptual design of the database.
Explain Logical Design Phase
Logical Design represents data in the form of relational model. ER diagram produced in the conceptual design phase is used to convert the data into the Relational Model.
Explain Physical Design Phase
In physical design, data in relational model is implemented using commercial DBMS like Oracle, DB2.
State the advantages of DBMS
Minimized redundancy and data inconsistency, Simplified Data Access, Multiple Data Views, Data Security, Concurrent Access to Data, Backup and Recovery
