17、n data volumesis expected, availability of, the same or compatiblesoftware on large machines should be considered.This is one of the most common misconceptionsabout database management systems that are used inpersonal computersThoroughly comprehensive andsophisticated business systems can be develop 。

18、ed indBASh, Paradox and other DBMSsHowever, theyare created by experienced programmers using theDBMSs own programming language. That is not the same as users who create and manage personal filesthat are not part of the mainstream company systemTransaction Management of DatabaseThe objective of long- 。

19、duration transactions is to model long-duration, interactive Database access sessions in application environmentsThe fundamental assumption about short-duration of transactions that underlies the traditional model of transactions is inappropriate for long-duration transactionsThe implementation of t 。

20、he traditional model of transactions may cause intolerably long waits when transactions aleph to acquire locks before accessing data, and may also cause a large amount of work to be lost when transactions are backed out in response to user-initiated aborts or system failure situations The objective。

21、of a transaction model is to pro-vide a rigorous basis for automatically enforcing criterion for database consistency for a set of multiple concurrent read and write accesses to the database in the presence of potential system failure situationsThe consistency criterion adopted for traditional trans 。

22、actions is the notion of scrializabilityScrializa-bility is enforced in conventional database systems through the use of locking for automatic concurrency control, and logging for automatic recovery from system failure situationsA transaction”that doesnt provide a basis for automatically enforcing d 。

23、ata-base consistency is not really a transaction. To be sure, a long-duration transaction need not adopt seri-alizability as its consistency criterionHowever. there must be some consistcricv criterionVersion System Management of Database Despite a large number of proposals on version support in the。

24、context of computer aided design and software engineering, the absence of a consensus on version semantics has been a key impediment to version support in database systemsBecause of the differences between files and databases, it is intuitively clear that the model of versions in database systems ca 。

25、nnot be as simple as that adopted in file systems to support software engineeringFor data-bases, it may be necessary to manage not only versions of single objects (e.g. a software module, document, but also versions of a collection of objects (e.g. a compound document, a user manual ， etcand perhaps e 。

26、ven versions of the schema of database (c.g. a table or a class, a collection of tables or classes)Broadly, there are three directions of research and development in versioningFirst is the notion of a parameterized versioning ， that is, designing and implementing a versioning system whose behavior may 。

27、 be tailored by adjusting system parameters This may be the only viable approach, in view of the fact that there are various plausible choices for virtually every single aspect of versioningThe second is to revisit these plausible choices for every aspect of versioning, with the view to discarding s 。

28、ome of themes either impractical or flawed. The third is the investigation into the semantics and implementation of versioning collections of objects and of versioning the database scheThere is no consensus of the definition of the term management information system. Some writers prefer alternative。

29、terminology such as information processing system, information and decision system, organizational information system, or simply information system to refer to the computer-based information processing system which supports the operations, management, and decision-making functions of an organization 。

30、. This text uses “MIS” because it is descriptive and generally understood;
it also frequently uses “information system” instead of “MIS” to refer to an organizational information system.2、A definition of a management information system, as the term is generally understood, is an integrated, user-mac 。

31、hine system for providing information to support operations, management, and decision-making functions in an organization. The system utilizes computer hardware and software;
manual procedures;
models for analysis planning, control and decision making;
and a database. The fact that it is an integrat 。

32、ed system does not mean that it is a single, monolithic structure;
rather, it means that the parts fit into an overall design. The elements of the definition are highlighted below. Computer-based user-machine system3、Conceptually, a management information can exist without computer, but it is the po 。

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