1、外文资料DATABASE MANAGEMENT SYSTEMS（DBMS）AND MANAGEMENT INFORMATION SYSTEM（MIS）You know that a database is a collection of logically related data elements that may be structured in various ways to meet the multiple processing and retrieval needs of organizations and individualsThere s nothing new about
2、databasesearly ones1 were chiseled in stone，penned on scrolls，and written on index cardsBut now databases are commonly recorded on magnetizable media，and computer programs are required to perform the necessary storage and retrieval operationsYoull see in the following pages that complex data relatio
3、nships and linkages may be found in all but the simplest databases2The system software package that handles the difficult tasks associated with creating，accessing，and maintaining database records is called a database management system（DBMS）The programs in a DBMS package establish an interface betwee
4、n the database itself and the users of the database（These users may be applications programmers，managers and others with information needs，and various OS programs）A DBMS can organize，process，and present selected data elements from the databaseThis capability enables decision makers to search，probe，a
5、nd query database contents in order to extract answers to nonrecurring and unplanned questions that arent available in regular reports3These questions might initially be vague and / or poorly defined，but people can“browse”through the database until they have the needed informationIn short，the DBMS w
6、ill“manage”the stored data items and assemble the needed items from the common database in response to the queries of those who arent programmersIn a file-oriented system，users needing special information may communicate their needs to a programmer，who，when time permits，will write one or more progra
7、ms to extract the data and prepare the information4The availability of a DBMS，however，offers users a much faster alternative communications path（see Fig. 7-1）If the DBMS provides a way to interactively and update the database, as well as interrogate it capability allows for managing personal data-Ac
8、es however, it does not automatically leave an audit trail of actions and does not provide the kinds of controla necessary in a multiuser organization. These-controls are only available when a set of application programs are customized for each data entry and updating function. Software for personal
9、 computers which perform me of the DBMS functions have been very popular arsenal computers were intended for use by individuals for personal information storage and process- These machines have also been used extensively small enterprises, professionals like doctors, acrylics, engineers, lawyers and
10、 so on By the nature of. intended usage, database systems on these machines except from several of the requirements of full doge database systemsSince data sharing is not：Tended, concurrent operations even less so, the) fewer can be less complex. Security and integrity7aintenance are de-emphasized o
11、r absent. As data-) limes will be small, performance efficiency Is also important. In fact, the only aspect of a database system that is Important is data Independence. Data-.dependence, as stated earlier. Means that applicant programs and user queries need not recognizantphysical organization of da
12、ta on secondary storage. The importance of this aspect, particularly for the personal computer user, is that this greatly simplifies database usage. The user can store, access and manipulate data at a high level (close to the application) and be totally shielded from the low level (close to the mach
13、ine) details of data organization. We will not discuss details of specific PC DBMS software packages hereLet us summarize in the following the strengths and weaknesses of personal computer data-base software systems： The most obvious positive factor is the user friendliness of the software. A user w
14、ith no prior computer background would be able to use the system to store personal and professional data, retrieve and perform relayed processing. The user should, of course, satiety himself about the quality of software and the freedom from errors (bugs) so that invest-merits in data arc protected.
15、 For the programmer implementing applications with them, the advantage lies in the support for applications development in terms of input screen generations, output report generation etcoffered by theses stems The main negative point concerns absence of data protection featuresUnless encrypted, data
16、 cane accessed by whoever has access to the machine Data can be destroyed through mistakes or maliciousintent. The second weakness of manv of the PC-basedsystems is that of performance. If data volumes growup to a few thousands of records，performance couldbe a bottleneck For organization where growth in data volumesis expected, availability of, the same or compatiblesoftware on large machines should be consider
