Hardly any computer or online ap­pli­ca­tion can work without a suitable database system. It’s precisely for this reason that it is certainly a good idea to go into a little more detail on this topic. Just as important as the data pool itself is an un­der­ly­ing database man­age­ment system, without which a database simply wouldn’t work.

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What is a DBMS?

A Database Man­age­ment System – DBMS for short – along with the data pool forms a database system (the general term ‘database’ is fre­quent­ly used for the latter). With such a DBMS there is generally software that de­ter­mines the model of a database system and is therefore the crucial component to even be able to construct, manage and use a database. Only once the database man­age­ment system has been installed and es­tab­lished can users add and read the data pool desired. Reading and writing per­mis­sions as well as general ad­min­is­tra­tive functions are made possible by ap­pli­ca­tion-specific in­ter­faces and an ap­pro­pri­ate database language. The most well-known of these languages is SQL (Structured Query Language).

Note
The terms ‘Database Man­age­ment System (DBMS)’ and ‘database’ are often wrongly conflated when de­scrib­ing the software that manages a data pool. In fact, the database is nothing more than the data pool in a struc­tured format, while the DBMS is the crucial component in im­ple­ment­ing these struc­tures.

What com­po­nents does a DBMS have?

A database man­age­ment system consists of various com­po­nents, all of which con­tribute to the software running smoothly. The DBMS can be broken down into three principal com­po­nents. These are the data dic­tio­nary, the data de­f­i­n­i­tion language and the data ma­nip­u­la­tion language.

  • Data dic­tio­nary: The data dic­tio­nary is a con­cen­tra­tion of metadata. This metadata contains in­for­ma­tion about the content of the different data in the data storage. It all serves as a source of in­for­ma­tion via the user au­tho­riza­tion for the data pools as well as the physical rep­re­sen­ta­tion. To put it simply, all relevant in­for­ma­tion about the data saved in a database is stored in the dic­tio­nary.
  • Data de­f­i­n­i­tion language: The data de­f­i­n­i­tion language (DDL) has the job of struc­tur­ing the contents of a database. In­di­vid­ual objects like ref­er­ences, re­la­tion­ships or user per­mis­sions can be changed, deleted and created with the help of the de­f­i­n­i­tion language.
  • Data ma­nip­u­la­tion language: Data sets contained in a database can be deleted, inserted, changed and read with the help of the data ma­nip­u­la­tion language (DML). This language also makes it possible to compress and extract this data.

Tasks, functions and re­quire­ments of Database Man­age­ment Systems

The database man­age­ment system is the most important component in a database system. Without the DBMS the data pool can neither be managed nor monitored. The software is also re­spon­si­ble for managing all reading and writing per­mis­sions for the database. One widely used term to describe the functions and re­quire­ments for trans­ac­tions in a database man­age­ment system is ACID, an acronym for atomicity, con­sis­ten­cy, isolation and dura­bil­i­ty. The terms within ACID cover the most important re­quire­ments for a DBMS:

  • Atomicity describes the ‘all or nothing’ property of DBMS, whereby only valid queries can take place in the correct sequence and so the entire trans­ac­tion is carried out correctly.
  • Con­sis­ten­cy requires suc­cess­ful trans­ac­tions to leave a stable database behind, making it necessary to con­stant­ly verify all trans­ac­tions.
  • Isolation is the term for the re­quire­ment that trans­ac­tions don't ‘get in each other’s way’, which is often guar­an­teed by certain locking functions.
  • Dura­bil­i­ty means that all data in the DBMS is stored per­ma­nent­ly, even after a suc­cess­ful trans­ac­tion is completed. This is also true, or es­pe­cial­ly so, for system errors or the DBMS mal­func­tion­ing. Trans­ac­tion logs that si­mul­ta­ne­ous­ly record all op­er­a­tions in the DBMS are essential to dura­bil­i­ty.

Below you can find a further breakdown of the functions and demands of a database man­age­ment system following the ACID model.

Function/demand Ex­pla­na­tion  
Storing data Databases store elec­tron­ic texts, documents, passwords and other in­for­ma­tion, which can be retrieved with queries.  
Editing data Most databases – depending on access per­mis­sions – allow the in­for­ma­tion stored to be edited directly.  
Deleting data Data sets contained within databases can be deleted com­plete­ly. In some cases, data that has been deleted can be retrieved, but in other cases the in­for­ma­tion is then gone forever.  
Managing metadata In­for­ma­tion in databases is mostly stored with metadata or metatags. These tidy up the database and make the search function possible, for example. Often, access per­mis­sions via metadata are also regulated.The data man­age­ment follows four fun­da­men­tal op­er­a­tions: Create, Read/Retrieve, Update and Delete. This concept, known as the ((CRUD principle websites/web-en­twick­lung/crud-die-wichtig­sten-Daten­bank­op­er­a­tio­nen/)), is the basis for the data man­age­ment.
Data security Databases must be secure so that unau­tho­rized in­di­vid­u­als can’t access the data stored. Along with a high-per­for­mance en­cryp­tion process, careful man­age­ment – par­tic­u­lar­ly by the main ad­min­is­tra­tor – is essential for data security. Data security generally means taking the technical pre­cau­tions to prevent the data being ma­nip­u­lat­ed or lost. It is a key concept of data pro­tec­tion.  
Data integrity Data integrity means that data within a database complies with certain rules to ensure that the data is correct and to define the business logic of the database. Only in this way can it be ensured that the database as a whole works con­stant­ly and con­sis­tent­ly. In re­la­tion­al database models there are four of these rules: Area integrity, entity integrity, ref­er­en­tial integrity and logical con­sis­ten­cy.  
Multi-user mode Database ap­pli­ca­tions permit access to the database from various devices. In multi-user mode, data security and the dis­tri­b­u­tion of per­mis­sions are fun­da­men­tal. One challenge for databases in multi-user mode is also how data can be kept con­sis­tent with si­mul­ta­ne­ous reading and writing per­mis­sions without seriously affecting per­for­mance.  
Query op­ti­miza­tion On the technical side, a database must process each query as optimally as possible in order to guarantee good per­for­mance. If a database goes ‘in different di­rec­tions’ with a data query, the general per­for­mance of the database system will suffer.  
Trigger and stored pro­ce­dures These processes are mini ap­pli­ca­tions stored inside database man­age­ment systems, which can be retrieved (‘triggered’) with certain change ac­tiv­i­ties. The aim of this is to improve data integrity, among other things. With re­la­tion­al databases, database triggers and stored pro­ce­dures are typical processes – the latter can also con­tribute to system security if users are only allowed to carry out ac­tiv­i­ties with pre­fab­ri­cat­ed pro­ce­dures.  
System trans­paren­cy System trans­paren­cy is par­tic­u­lar­ly relevant in dispersed systems: By keeping the data dis­tri­b­u­tion and im­ple­men­ta­tion from the user, using the dis­trib­uted database is then the same as with a cen­tral­ized database. Different grades of system trans­paren­cy reveal or conceal back­ground processes. The necessary function, however, is to make it as simple as possible to use.  
Note

If you are operating your own database, com­pre­hen­sive data security is extremely important!

What types of DBMS / database models are there?

A database man­age­ment system is installed on a system in order to be able to manage data sets optimally. As already mentioned, here there are various models that primarily differ in the intended struc­tur­ing of the data. The choice of DBMS, therefore, also means de­ter­min­ing a database model. The following database models are available to choose from:

  • Re­la­tion­al
  • Hi­er­ar­chi­cal
  • Network-oriented
  • Object-oriented
  • Document-oriented

The most widely used and most popular is the re­la­tion­al database model. In this model, the data is struc­tured in table rows. The advantage of this is the pos­si­bil­i­ty of creating certain re­la­tion­ships between the in­di­vid­ual rows and rep­re­sent­ing these in columns. The approach with a hi­er­ar­chi­cal database model is different: Here, the different data interacts in parent-child re­la­tion­ships, and so it is struc­tured in a hi­er­ar­chi­cal system.

The network-oriented database model rep­re­sents another approach to or­ga­niz­ing data. Here, the data is struc­tured inside a network. The object-oriented database model works in a different way. Alongside the re­la­tion­ships between the data sets, heredity also plays an important role here. In this way, objects – regulated by the DBMS – can transmit prop­er­ties to other objects.

Database models that work in a document-oriented way envisage the storage of data sets in different documents.

Database Man­age­ment Systems: An overview of ad­van­tages and dis­ad­van­tages

As the cor­ner­stones of databases, database man­age­ment systems are char­ac­ter­ized by different strengths and ad­van­tages. Like with any other software, though, DBMS also have various weak­ness­es, as the following list of ad­van­tages and dis­ad­van­tages makes clear.

Ad­van­tages of a Database Man­age­ment System:

  • easy man­age­ment of large data sets
  • easy, effective access to stored data
  • high flex­i­bil­i­ty
  • data integrity and con­sis­ten­cy
  • access control for users (data security and pro­tec­tion)
  • high avail­abil­i­ty

Dis­ad­van­tages of a Database Man­age­ment System:

  • rel­a­tive­ly expensive initial in­vest­ment (incl. ad­di­tion­al costs for hardware)
  • less efficient for special software
  • requires qualified employees (database ad­min­is­tra­tors)
  • higher vul­ner­a­bil­i­ty due to the data being cen­tral­ized

Examples of DBMS: The most popular Database Man­age­ment Systems

A range of different database man­age­ment systems are available. Here you can find the 15 most popular and widely used DBMS:

  • Microsoft Access – re­la­tion­al
  • Microsoft SQL Server – re­la­tion­al
  • MySQL – re­la­tion­al
  • Oracle Database – re­la­tion­al
  • OrientDB – document-based
  • CouchDB – document-based
  • Db2 (IBM) – re­la­tion­al
  • IMS (IBM) – hi­er­ar­chi­cal
  • IBM Informix – re­la­tion­al
  • MariaDB – re­la­tion­al
  • Sybase ASE – re­la­tion­al
  • MongoDB – document-oriented
  • Post­greSQL – object-re­la­tion­al (Mix of re­la­tion­al and object-oriented ap­proach­es)
  • Firebird – re­la­tion­al
  • In­ter­Sys­tems Caché – object-re­la­tion­al (Mix of re­la­tion­al and object-oriented ap­proach­es)
  • In­ter­Sys­tems IRIS – object-re­la­tion­al (Mix of re­la­tion­al and object-oriented ap­proach­es)
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