A schema separates the physical aspect of data storagefrom the logical aspects of data representation.
A schema separates the physical aspect of data storagefrom the logical aspects of data representation.
A logical unit of data is a virtual representation of data while a physical unit of data is the actual storage of data on a physical device. The logical unit of data is how data is organized and manipulated from a software perspective, while the physical unit of data is how data is stored on hardware such as disks or memory.
A logical representation of one or more physical disks configured to provide redundant and/or large storage space for the system.
folder
Logical design refers to the abstract representation of the data and the relationships among data elements, focusing on how data is organized and accessed without considering the physical storage details. In contrast, physical design involves the actual implementation of the logical design, specifying how data will be stored on hardware, including file structures, indexing methods, and data storage formats. Essentially, logical design is about "what" data is needed and "how" it relates, while physical design deals with "where" and "how" that data is physically stored and retrieved.
It is generally considered more difficult to achieve logical data independence compared to physical data independence. Logical data independence involves separating the conceptual structure of the data from the physical storage aspects, which can be complex depending on the database design. Physical data independence primarily deals with shielding the application from changes in the storage structure, which is usually more straightforward to achieve.
difference between physical and logical data flow diagrams.
logical
Tree
Yes, a physical topology can support multiple logical topologies.
* Physical file (PF) contains the data and have only one record format. Logical file (LF) is a view of the physical file which does not contain any data may be based on one physical file or more then one physical file. Logical file can have more then one record format. Logical can be non join or join logical file. Performance becomes better if you use the logical file in the program.
token ring uses a physical star and a logical ring ,while FDDI uses a physical star/ring and a logical ring.