Distributed Database Management System(DDBMS) Components
The different components of DDBMS are as follows:
• Computer workstations or remote devices (sites or nodes) that form the network system. The distributed database system must be independent of the computer system hardware.
• Network hardware and software components that reside in each workstation or device. The network components allow all sites to interact and exchange data. Because the components—computers, operating systems, network hardware, and so on—are likely to be supplied by different vendors, it is best to ensure that distributed database functions can be run on multiple platforms.
Evoluation of DDBMS
Distributed Processing and Distributed Databases
Advantages and Disadvantages of DDBMS
• Communications media that carry the data from one node to another. The DDBMS must be communications media-independent; that is, it must be able to support several types of communications media.
• The transaction processor (TP), which is the software component found in each computer or device that requests data. The transaction processor receives and processes the application’s data requests (remote and local). The TP is also known as the application processor (AP) or the transaction manager (TM).
• The data processor (DP), which is the software component residing on each computer or device that stores and retrieves data located at the site. The DP is also known as the data manager (DM). A data processor may even be a centralized DBMS.
The following Figure illustrates the placement of the components and the interaction among them. The communication among TPs and DPs shown in the figure is made possible through a specific set of rules, or protocols, used by the DDBMS.
The protocols determine how the distributed database system will:
• Interface with the network to transport data and commands between data processors (DPs) and transaction processors (TPs).
• Synchronize all data received from DPs (TP side) and route retrieved data to the appropriate TPs (DP side).
• Ensure common database functions in a distributed system. Such functions include security, concurrency control, backup, and recovery.
Distributed Database Design Concepts
