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What is magnetic disks?explain it?
Magnetic disk provides the bulk of secondary storage of modern computer system. The disk capacity is growing at over 50% per year. But the storage needs of large applications have also been growing very fast and in some case each faster than the growth rate of disk capacities. A large data base may need 100 of disks.
Physical characteristics of disk
Physical disks are relatively simple. Every disc platter has a flat circular shape
We can call magnetic disk as
Ø hard disk
Ø Floppy disk
The read write head keeps information on a sector magnetically as reversals of the direction of magnetization of the magnetic material. There might be hundreds of concentric tracks on a disc surface, having thousands of sectors.
Differentiate between Key and superkey? Key and superkey - A key a single attribute or a combination of two or more attributes of an entity set in which is used to identify o
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There are three main sources of utilities and applications for a DBMS: a. Vendor applications and utilities are given for working with or maintaining the database, and generally
Define union compatibility? Explain why INTERSECTION of two relations cannot be performed if they are not union compatible? Two relations R(A1, A2,-------, An) and S(B1, B2,--
A collection of a same kind of entities is known as an Entity Set or entity type. Example: For the COLLEGE database defines earlier objects of concern are Students, Faculty,
Failures and Recovery In practice various things might occur to prevent a transaction from completing. Recovery methods are used to bring database, which does not satisfy consi
You are required to implement integrity constraints within the database to enforce the following requirements: For Projects: Start date must be supplied. Start date cannot be i
How to Insert data in your table from another table? insert into e.g, To insert tuples from employee into N_emp created above, use following statement Insert into N_emp
complete er diagram of textile industry management
What is DAG? The class-subclass relationship is shown by a directed acyclic graph.eg: employees can be temporary or permanent. We might be create subclasses temporary \and perm
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