1.5 - While the use of computers for data management was a...

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While the use of computers for data management was a serious improvement over the manual data management, many problems arose. First of all, it required computer specialists to design, program and modify the system. The administration of the files was complex and difficult. For this reason it cannot perform ad-hoc queries. Presenting both structural and data dependency (as we will discuss later) the modification of the files was very complicated which lead to redundant and inconsistent data. 1
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One of the problems for the file system is structural dependence. This means that in order to access a file you need to know the file structure (for instance which are the fields, size of a record). When a modification to the structure is needed, as in this example to add the customer date of birth, you will need to modify the entire file (by coping the entire file into a new one that will contain also space for this field). Also, you will need to update all your application programs that are using this file, because their access to the file will be changed. A database management system is structural independent, which means that you can modify the structure of the files involved (for instance adding or removing fields) without needing to modify the application programs. This is one of the advantages to use a DBMS 2
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A similar problem is related to the characteristics of a given field. Suppose that you have a field that is currently storing a name of maximum 40 characters, and you need to extend the size of the field to be able to store 60 characters. In the file system you will need to go through the same process as for a structural change. You will need to modify all your programs to update how they are reading the modified data field. This problem of the file systems is called data dependence. A DBMS is data independent. You can modify the characteristics associated with a
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This note was uploaded on 01/22/2011 for the course IT 214 taught by Professor Staff during the Spring '08 term at George Mason.

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1.5 - While the use of computers for data management was a...

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