Databases. Single user and multi user systems

Single user and multi user systems. The concept of centralized data management


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1. The concept of single-user and multi-user database systems. Advantages of use

Database systems are divided into two types:

  • single user. In these systems, only one user has access to data at a time. This property can be a significant disadvantage compared to multi-user systems;
  • multiuser. Here it is allowed to work with the database of several (many) users at the same time. Such systems have a number of advantages over single-user systems. However, a multi-user system is more difficult to implement.

Compared to conventional (paper) accounting, single-user and multi-user database systems have a number of obvious advantages:

  • a significant reduction in labor costs. There is no need for mechanical routine accounting work. The use of modern programs with a convenient user interface greatly facilitates database maintenance;
  • processing speed. The sampling speed of a computer is much faster than a human. Especially this advantage becomes more relevant with the increase of the database. The use of computers allows you to get the necessary information from the database in the blink of an eye;
  • reduction of errors in accounting. Modern database software is built in such a way that human errors are automatically identified and options for correcting them are proposed;
  • compactness. One laptop or other digital device can contain as much information as will fit in thousands of voluminous file cabinets;
  • relevance. The information is always up to date.

An additional and most significant advantage of a multi-user database system is the provision of centralized data management.


2. Centralized data management in the enterprise. Basic concepts. Data administrator and database administrator

Centralized data management makes sense in multi-user environments or systems. In these systems, the database is maintained by several users with different types of privileges (opportunities). In the modern information society, the effective management of any association of people is ensured precisely by multi-user database systems.

The concept of centralized management assumes that the organization maintaining the database has a so-called data administrator. The data administrator has primary responsibility for enterprise data and understands the needs of the organization at the management level. The data administrator belongs to the management personnel.

Data administrator:

  • decides on entering the necessary data into the database;
  • defines the requirements for maintaining and processing the entered data;
  • defines a list of persons who have access to perform a certain set of data operations;
  • provides data protection from unauthorized access, etc.

The data administrator must have an understanding of the capabilities of databases at a technical level. The data administrator gives instructions to the technical specialist, who is the database administrator (DBA).

A database administrator is a highly qualified specialist who is able to perform the following tasks at a professional level:

  • creation of a database;
  • ensuring technical control over the operation of the database;
  • solution “on the fly” of various tasks that arise during the operation of the database. Examples of such tasks are maintenance of the database system, ensuring the necessary speed, etc.

To ensure the full functioning of the database, the database administrator is provided with a staff consisting of programmers and assistants. The entire team of specialists must ensure the uninterrupted long-term operation of the organization’s database.


3. Benefits of a centralized approach to data management

In multi-user databases, it is especially important to provide a centralized approach to data management. This approach involves the simultaneous use of the database by several users. Centralized database management provides the following benefits:

  1. Ensuring data sharing. This assumes that the data can be accessed by multiple applications, the number of which can be expanded without making any changes to the database.
  2. Reduction of data redundancy. The data is shared between different applications. There is no need to create unnecessary auxiliary information files for the operation of each application. The information in these files can be duplicated, resulting in inefficient use of secondary storage. With centralized management, the data administrator describes the specifics of using certain data by different applications, taking into account the ability to make subsequent “updates” of them.
  3. Ensuring data inconsistency. Data inconsistency occurs when there are two records in the database that contradict each other. In other words, these records are inconsistent. Any DBMS controls such situations when adding new or changing existing data. If an update is made to one entry, it will automatically propagate to all others. This process is called propagating updates.
  4. Support for transactions. A transaction is a unit of work that performs one or more operations in a database (for example, transferring money from one account to another). One of the advantages of using transactions is the correct execution of operations in the database in the event of unforeseen situations (for example, failures due to a power outage).
  5. Ensuring data integrity. This means that the data in the database must be guaranteed to be correct. Correctness is understood as the presence of consistent records about one fact (see point 3 – ensuring data inconsistency). The information in the database must also be correct. An example of incorrect information is the setting of the teacher’s daily norm at 30 hours, although the day has 24 hours. In order for the information to be correct, the data administrator defines so-called business rules or, in other words, integrity constraints. Any attempt to enter incorrect information will be corrected by these restrictions.
  6. Setting data protection. In centralized database systems with access to data of many users, a reliable system of protection must be implemented. In this system, the database administrator implements so-called security constraints. These restrictions imply the use of different types of access to each element of information during its processing (data insertion, data editing, etc.).
  7. Ensuring a rational balance of distribution of database resources. This refers to setting the database structure in such a way that the service for the entire organization is the best (fastest). For example, the correct allocation of secondary memory in order to provide fast access to information by the most used applications (even with a loss of performance in other applications). This is all implemented by the database administrator in consultation with the data administrator.
  8. Support standardization. The database administrator (DBA), at the direction of the data administrator (AD), implements support for all the necessary standards that streamline (regulate) the presentation of data in the system. There are private, corporate, departmental, industrial, national and international standards. With the help of standardization, the coordination of data transfer between different systems is ensured, especially in the case of distributed systems. The standards define the sharing, naming and documentation of data.


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