A Database is a collection of data that represents the information of interest to an information system.
In technology, there is a collection of data managed by aDBMS.
In a common database data resides on disk (secondary storage).
The DBMS has the task of interfacing the data with the user. If the data is organized the DBMS will be faster on meeting the needs of users.
The database can be shared, even though this leads to problems of competition, in the case where the users arewriters. In fact, most writers can not work simultaneously with each other or with readers as thiswould lead to reads / writes incorrect data.
The DBMS has the task of ensuring reliability even in case of multiple writers. To do this, normally the database is managed on a competitive basis, except when you need to write, when you restrict access to just as interested in mutual exclusion.
The reliability of the DBMS is important to ensure thatmechanisms are used for backup / recovery mechanismsand logs, which record all the changes to allow backtrack.
The data model shows how the data are represented.
The most common technique is to organize tabularrelational. Relational, from versatility, tabular, no need to know the type of each data. Queries to the DBMS varydepending on its internal organization.
A DBMS (Data Base Management System) is a software system to manage the collection of data that are large,shared and persistent, ensuring their privacy andaffifabilità.
So, a DBMS (Data Base Management System) is a software system to manage the collection of data that are large,shared and persistent, ensuring their privacy andaffifabilità.
The characteristics of a DBMS are:
- Much larger main memory available;
- Sharing data between applications and users;
- Data persistence;
- Reliability of data in case of hardware failures and software;
- Privacy of data;
Disadvantages of DBMS:
- Products are expensive, complex and require direct investment (purchase of the product) and indirect investments (personal training and conversionapplications);
- Provide a set of services in an integrated manner.