[قلم صريح]

• Advantages of dbms
It means all of the information is together.
The information is easy to access at any time.
It's more easily retrievable.
Many people can access the same database at the same time.
Improved data security.
Reduced data entry, storage, and retrieval costs.

DISADVANTAGES…
Database systems are complex, difficult, and time-consuming to design.
Initial training required for all programmers and users.
Suitable hardware and software start-up costs.
A longer running time for individual applications.
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Advantages and disadvantages of relational DBMS :

the most flexible of the database models

no obvious match of implementation to model - model is the user's view,
not the way the data is organized internally

is the basis of an area of formal mathematical theory

most RDBMS data manipulation languages require the user to know the contents of relations,
but allow access from one relation to another through common attributes
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Advantages of Object relational DBMS :
The main advantages of extending the relational data model come from reuse and sharing.
Reuse comes from the ability to extend
the DBMS server to perform standard functionality centrally,
rather than have it coded in each application.
If we can embed the functionality in the server,
it saves having to define it in each application that needs it, and consequently allows the functionality to be shared by all applications
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Advantages and disadvantages of Distributed DBMS

The information system manager must make decisions on whether to use centralized or de-centralized databases based on a number of issues including the following:

* Decentralized databases exchange files and therefore may exchange corrupted files or viruses that may affect the entire system. Security of these databases are difficult to maintain. Though the section on Data-less information systems discusses how these systems can be used to create more confidential information exchanges.
* In decentralized databases the type of data to be exchanged, the process of addressing the data, and the protocol for updating the data must be agreed upon ahead of time and plans must be in place for updating the process.
* In centralized databases lack of backup or inadequate back up may result to complete loss of data while in distributed data systems data loss is limited to nodes affected.
* De-centralized databases are more flexible and allow different units to update and maintain their own data. At the same time, this increased flexibility runs the risk that some units may institute changes that may make them less accessible by others.
* When different groups and systems are involved in maintaining the data, then there is more opportunity for differences in quality of data to emerge. A decentralized database needs to have procedures for determining the quality (accuracy, recency, reliability, etc.) of the data.d