What is distributed data dictionary and how does it work?

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What is distributed data dictionary and how does it work?

A distributed data dictionary is a component of a distributed database system that stores and manages metadata information about the data stored across multiple nodes or sites in the distributed environment. It serves as a central repository for storing information about the structure, organization, and relationships of the data distributed across different database instances.

The distributed data dictionary works by maintaining a global view of the distributed database system. It stores metadata information such as table definitions, attribute details, integrity constraints, access privileges, and other relevant information about the data stored in each database node. This information is crucial for ensuring data consistency, integrity, and efficient query processing in a distributed environment.

When a user or application initiates a query or transaction, the distributed data dictionary is consulted to retrieve the necessary metadata information. It provides the necessary details about the location of the data, the structure of the tables, and the relationships between them. This information is used by the query optimizer to generate an optimal query execution plan.

In a distributed database system, data may be distributed across multiple nodes or sites, and each node may have its own local data dictionary. The distributed data dictionary ensures that all local data dictionaries are synchronized and consistent with each other. It facilitates the coordination and communication between different nodes by providing a global schema definition and resolving any conflicts or inconsistencies that may arise due to data distribution.

The distributed data dictionary also plays a crucial role in data integrity and security. It enforces access control policies by storing information about user privileges and permissions. It ensures that only authorized users can access and modify the data stored in the distributed database system.

Overall, the distributed data dictionary acts as a central repository of metadata information in a distributed database system. It provides a global view of the data and ensures consistency, integrity, and efficient query processing in a distributed environment.