DBMS: software application that is used to create, maintain, and provide controlled access to user databases
Metadata is data that describes the properties or characteristics of other data. It allows database designers and users to understand what the data means.
Disadvantages of flat files
- Two users modifying information at the same time
- Programs using the file must know the format of the file
- We can store only limited types of elements, mainly text
The information resides in database structures (e.g. tables), and applications access the information through the DBMS.
Complex application interface
Difficult to control concurrent access
Program-data dependence: the program needs to know the format of the data
Duplication of data
Data may be difficult to locate
Difficult data sharing
Lengthy development times
Excessive program maintenance (e.g. changing the data format means all applications have to change, at the same time)
Represents users view of data (e.g. reports, queries)
Emphasis on integration and sharing of data
Reduces data redundancy
Eliminates inter-dependence between programs and data
Improved data quality
Increased productivity of application development
Reduced program maintenance
Easier to extract information
Security is improved
Integrity can be assured
Installation and management costs
Complexity of DBMS
Powerful hardware needed to handle load
Need for explicit backup and recovery
Applications may be dependent of specific DBMS platforms or versions
Initial cost for implementation may be large
Examples of databases: customer database, flights database, CDs databases, product databases, books database, billing database, students database, movies database.
When there is a need to store records of something (e.g. students, bank accounts, eBay items) we can create a database.
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