Table of Contents
What is the difference between physical and logical?
Difference between the physical and logical address The logical address does not exist physically in the memory hence it is sometimes known as virtual address whereas the physical address is a location in the memory unit. The logical address is used as a reference to access the physical address.
How many logical views can a database support?
three logical views
What is physical structure of database?
Introduction to Physical Storage Structures. A data file is a physical file on disk that was created by Oracle Database and contains data structures such as tables and indexes. A temp file is a data file that belongs to a temporary tablespace.
What is logical level in 3 tier DBMS?
Conceptual level It is also called logical level. The whole design of the database such as relationship among data, schema of data etc. are described in this level. Database constraints and security are also implemented in this level of architecture. This level is maintained by DBA (database administrator).
What is the difference between logical and physical models?
The main difference between Logical and Physical Data Model is that Logical data models help to define the data elements and their relationships, while the physical data models help to design the actual database based on the requirements gathered during the logical data modelling.
What are the two components of a logical data model?
The components of a logical data model include Entities, Relationships, and Attributes. Each Entity represents a set of persons, things, or concepts about which the business needs information. Each Relationship represents an association between two entities.
What is a logical data format?
A logical data model or logical schema is a data model of a specific problem domain expressed independently of a particular database management product or storage technology (physical data model) but in terms of data structures such as relational tables and columns, object-oriented classes, or XML tags.
What is the logical view of data quizlet?
The logical view of data is: How people organize, view, and understand relationships among data items. A schema is defined as: description of data elements in a database, relationships among them, and logical model used to organize and describe data.
What is a logical view of data?
A logical view of data is a data model in an enterprise. A logical data object model contains logical data objects. A logical data object is an object that describes a logical entity in an organization, such as a customer or an order. It has attributes and keys, and it describes relationships between attributes.
Which level is responsible for logical structuring of database?
The conceptual level is at a higher level than the physical level. It is also known as the logical level. It describes how the database appears to the users conceptually and the relationships between various data tables. The conceptual level does not care for how the data in the database is actually stored.
What is logical flow?
What is logical flow? The writing skill of ‘logical flow’ can be defined as all the aspects of your writing that help the reader move smoothly from one sentence to the next, and one paragraph to another. So it is with the flow of your sentences.
Is a classical approach to database design?
There are two classical approaches to database design: Top-down design starts by identifying the data sets and then defines the data elements for each of those sets. This process involves the identification of different entity types and the definition of each entity’s attributes.
What is the difference between logical and physical middleware models?
There are two types of middleware models: logical and physical. The logical middleware model depicts how information moves throughout the enterprise conceptually. In contrast, the physical middleware model depicts both the actual method of information movement and the technology employed.
Which of the following is logical database structure?
Logical structures include tablespaces, schema objects, data blocks, extents and segments. Database is logically divided into one or more tablespaces. Each tablespace creates one or more datafiles to physically store data. Schema objects are the structure that represents database’s data.
What does a logical data model look like?
A logical data model describes the data in as much detail as possible, without regard to how they will be physical implemented in the database. Features of a logical data model include: Includes all entities and relationships among them. All attributes for each entity are specified.
How is primary key represented in ER diagram?
The primary key is a candidate key that is selected by the database designer to be used as an identifying mechanism for the whole entity set. It must uniquely identify tuples in a table and not be null. The primary key is indicated in the ER model by underlining the attribute.
What is physical and logical database?
A logical database must be able to access and identify all files within the storage system to operate correctly, whereas a physical database manages a much smaller field of information. Sometimes, a physical database stores only a single file with one value or word in it.
What is logical data model with example?
For example, a simple logical data model for a retail company can organize all necessary facts by store, product, and time, which are three common business perspectives typically associated with a retail business. Logical data models are independent of a physical data storage device.