What is difference between logical and physical files?
Physical files contain the actual data that is stored on the system, and a description of how data is to be presented to or received from a program. Logical files do not contain data. They contain a description of records found in one or more physical files.
What are logical files?
Logical files do not contain data. They contain a description of records that are found in one or more physical files. A logical file is a view or representation of one or more physical files. Logical files that contain more than one format are referred to as multi-format logical files.
What is the difference between PF and LF?
It loads itself at run time as per the defined access path. 2. A logical file can contain up to 32 record formats. If there is a logical file for a PF, the LF can be deleted without deleting the PF.
What is file distinguish between logical and physical deletion of records and illustrate it with an example?
They contain a description of records that are found in one or more physical files. A logical file is a view or representation of one or more physical files….Logical File –
| Physical File | Logical File |
|---|---|
| It occupies the portion of memory. It contains the original data. | It does not occupy memory space. It does not contain data. |
What is physical and logical data independence?
Logical data independence: The ability to change the logical (conceptual) schema without changing the External schema (User View) is called logical data independence. Physical data independence: The ability to change the physical schema without changing the logical schema is called physical data independence.
What is logical and physical 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 level in database?
Conceptual 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 meant by physical schema?
Physical schema is a term used in data management to describe how data is to be represented and stored (files, indices, et al.) in secondary storage using a particular database management system (DBMS) (e.g., Oracle RDBMS, Sybase SQL Server, etc.). That is the domain of the physical schema.
How do you create a physical schema?
To Create an Physical Schema:
- Select the Data Server, right click and select Insert Physical Schema.
- If the technology supports multiple schemas:
- Check the Default box if you want this schema to be the default one for this data server (The first physical schema is always the default one).
- Go to the Context tab.
What are the types of schema?
Types of schemas
- Role schema.
- Object schema.
- Self-schema.
- Event schema.
What are examples of physical models?
A physical model (most commonly referred to simply as a model but in this context distinguished from a conceptual model) is a smaller or larger physical copy of an object….Some of the examples of Physical models:
- Model airplane.
- Model car.
- Model railway.
- Model rocket.
- Model house.
What is an example of physical data?
A physical data model is a database-specific model that represents relational data objects (for example, tables, columns, primary and foreign keys) and their relationships.
How do you convert logical data model to physical?
To transform a logical data model into a physical data model:
- Select a logical data model or a logical data model object in the Data Project Explorer.
- Click Data > Transform > Physical Data Model from the main menu.
- If the Check Model page is displayed, select the appropriate options:
How do you convert logical data model to physical in ERwin?
Transforming to physical with ERwin
- Go to Action > Design Layer > Derive New Model.
- In the Target Model section select the Physical radio button.
- In the Target Model tab, select Physical and specify the correct database and version.
- Click Next.
- In the Object Selection tab, select the relevant subject areas.
What is the relationship between the logical and physical models?
The logical model and the physical model are separate models. The logical model enables you to represent business information and define business rules. The physical model enables you to focus on the physical implementation of the model in a database.
Is an ERD a logical model?
Logical database modeling includes; ERD, business process diagrams, and user feedback documentation; whereas physical database modeling includes; server model diagram, database design documentation, and user feedback documentation. Conceptual Schema – covers entities and relationships.
What is the difference between logical and physical database design?
Logical database modeling is mainly for gathering information about business needs and does not involve designing a database; whereas physical database modeling is mainly required for actual designing of the database.