Lecture
A database user is a natural or legal person who has access to the database and uses the services of an information system to obtain information. Categories: - end user; - DB administrator; - developers and application administrators.
Multi-user database issues:
A natural consequence of the development of a DBMS is the problem of organizing the joint work of several users with the same set of data, or the problem of multi-user data access.
First of all, the situation of sharing the same set of data between multiple users can lead to conflicts (an attempt to change the same record one-time, a coincidence of reading and deleting information, etc.).
From the point of view of the organization of joint access to data from several users, the modes of work with them are divided into the mode of exclusive (exclusive) access and the mode of general (divided) access.
The mode of exclusive access to the database provides that only one of the users (software processes) can work with it, and the possibility of its opening by other users (processes) is blocked. Opening a database in exclusive mode, as a rule, is used to perform operations on changing the structure of tables and relations between them, exporting large amounts of information, performing maintenance operations on data (saving, restoring, compressing)
Accordingly, in the mode of shared access, several users can work with the database at once. To prevent possible conflicts when different users attempt to change the same records in the DBMS, a locking mechanism is used. Blocking an object in the event that a user works with it means preventing any other attempts to change this object, but at the same time it remains possible to read it. Thus, the locking mechanism provides more flexibility for manipulating data in comparison with the exclusive access mode.
A database administrator is a person or group of persons responsible for the development of database requirements, its design, creation, effective use and maintenance.
Basics administrator:
- domain analysis
- designing the database structure
- setting integrity constraints when describing the database structure
- initial loading and maintenance of the database
- data protection
- ensuring recovery of the database
- analysis of user requests
- analysis of the effectiveness of the functioning of the database
- work with end users
- preparation and maintenance of system Wed
- organizational and methodical work on database design
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Databases, knowledge and data warehousing. Big data, DBMS and SQL and noSQL
Terms: Databases, knowledge and data warehousing. Big data, DBMS and SQL and noSQL