What are the characteristics that distributed database systems do not have?

A characteristic that distributed database systems do not have is data redundancy.

Let’s take a look at the characteristics of distributed database systems:

1. Independence and transparency

Data independence is the main pursuit of database methods One of the goals, distribution transparency, means that users do not have to care about the logical partitions of the data, the details of the physical location distribution of the data, the consistency of duplicate copies (redundant data), and what database supports on the local site. a data model.

The advantages of distribution transparency are obvious. With distribution transparency, user applications can be written as if the data were not distributed. Applications do not have to be rewritten when data is moved from one site to another. When adding duplicate copies of certain data, there is no need to rewrite the application program. Data distribution information is stored in the data dictionary by the system, and user access requests for non-local data are interpreted, converted, and transmitted by the system based on the data dictionary.

2. Centralized node combination

The database is a resource shared by users. In a centralized database, in order to ensure the security and integrity of the database, the shared database is controlled. It is centralized and has a DBA responsible for supervising and maintaining the normal operation of the system. In a distributed database, there are two levels of data sharing:

The first is local sharing, that is, the shared data of each user on the local site is stored in the local database. These data are commonly used by users at the local site.

The second is global sharing, that is, each site of the distributed database also stores data that can be shared by users in other sites on the network to support global applications in the system.

3. Replication Transparency

Users do not need to care about the replication of the database at each node in the network, and the update of the replicated data is automatically completed by the system. In a distributed database system, data from one site can be copied to other sites for storage. Applications can use the copied data to complete distributed operations locally, avoiding data transmission through the network and improving system operation and query efficiency. However, the update operation of replicated data involves updating all replicated data.

4. Ease of scalability

In most network environments, a single database server will eventually become unsatisfactory. If the server software supports transparent horizontal scaling, then multiple servers can be added to further distribute data and share processing tasks.

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