Distributed database management system

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A distributed database management system is a database management system (DBMS) that has a degree of autonomy, heterogeneity, and distribution. Depending on the characteristics of these three criteria in one, different distributed DBMS can be distinguished.

Examples of distributed DBMS are master-slave systems, client-server systems (poorly distributed) and peer-to-peer systems (widely distributed).

autonomy

The autonomy of a (distributed) database management system describes the degree to which different interconnected DBMS can operate independently of one another. Independent decisions can be made in terms of design, communication and execution. A high degree of autonomy usually leads to a growing heterogeneity due to different decisions.

A distinction is made between the following autonomies:

  • The communication autonomy of a distributed database (VDB) refers to the ability to decide how to communicate with other parts of the database.
  • The embodiment autonomy refers to the ability of a portion of the VDB, local operations without the action of external operations of other parts to carry out and to determine the execution order itself.
  • The association autonomy of a part of the VDB implies that it can decide whether and to what extent it shares its functionality and resources with other parts.

If there is a high degree of autonomy, one speaks of a federated DBMS or a “ federated database ” as opposed to an integrated database. The term “federated” instead of “distributed” emphasizes that the systems were created independently of one another, while a highly distributed system can also have been designed from autonomous components.

Heterogeneity

With a high degree of homogeneity one speaks of a homogeneous DBMS , i. H. the systems used are essentially similar or identical. A trivial example of this is an asymmetrical distributed system ( client-server system ) consisting of personal computers on which the same operating system is operated and which without exception operate the same database application.

In contrast, there are also heterogeneous DBMS . These use different systems and applications accordingly. One example of this are hospital information systems , because depending on the respective departments (laboratory, patient administration, accounting, duty scheduling), a wide variety of data (images, sound, text, etc.) is generated. The programs used - especially in university hospitals - are mostly special developments that are not used beyond the defined area of ​​responsibility (each department uses its own software). For this reason, computer scientists are commissioned to plan, develop and maintain such systems in larger clinics.

Implementations

In the 1980s there were already prototypes of functional distributed databases, but at that time there was the problem that network protocols were seldom standardized, so that the implementations could only run under very specific environments.

Some developments that at least partially contain functions of distributed database systems are:

literature