Functions of Distributed Database System

Distribution basically leads to increased complexity in the system design and implementation. This is to achieve the potential advantages such as:

1. Network Transparencies
2. Increased Reliability
3. Improved Performance
4. Easier Expansion

Function of Centralized DBMS:

1. The basic function of centralized DBMS is that it provides complete view of our data. For example, we can have the query for the number of customers who are willing to buy worldwide.
2. The second basic function of Centralized DBMS is that it is easy to manage than other distributed systems.

The Distributed Database must be able to provide the following function in addition to those of a centralized DBMS’s. Functions of Distributed database system:

1. Keeping track of data – The basic function of DDBMS is to keep track of the data distribution, fragmentation and replication by expanding the DDBMS catalog.
2. Distributed Query Processing – The basic function of DDBMS is basically its ability to access remote sites and to transmits queries and data among the various sites via a communication network.
3. Replicated Data Management – The basic function of DDBMS is basically to decide which copy of a replicated data item to access and to maintain the consistency of copies of replicated data items.
4. Distributed Database Recovery – The ability to recover from the individual site crashes and from new types of failures such as failure of communication links.
5. Security – The basic function of DDBMS is to execute Distributed Transaction with proper management of the security of the data and the authorization/access privilege of users.
6. Distributed Directory Management – A directory basically contains information about data in the database. The directory may be global for the entire DDB, or local for each site. The placement and distribution of the directory may have design and policy issues.
7. Distributed Transaction Management – The basic function of DDBMS is its ability to devise execution strategies for queries and transaction that access data from more than one site and to synchronize the access to distributed data and basically to maintain the integrity of the complete database.

But These function basically increases the complexity of a DDBMS over centralized DBMS.

   A distributed database system is a collection of multiple interconnected databases that are geographically distributed across different sites. The functions of a distributed database system are:

1. Data distribution: One of the primary functions of a distributed database system is to distribute data across multiple sites. This is done to ensure that data is stored closer to where it is needed and to reduce the amount of data that needs to be transferred over the network.
2. Data replication: In a distributed database system, data can be replicated across multiple sites. Replication can improve system availability and reliability by ensuring that data is available even if one of the sites fails.
3. Data fragmentation: Data fragmentation involves breaking down a large database into smaller fragments and distributing them across multiple sites. This can help improve system performance by reducing the amount of data that needs to be transferred over the network.
4. Query processing: Query processing involves processing user queries and retrieving data from the distributed database system. This is a complex task as data may be stored across multiple sites and may need to be combined to answer user queries.
5. Transaction management: In a distributed database system, transactions may span multiple sites. Transaction management involves coordinating these transactions and ensuring that they are executed correctly and efficiently.
6. Security and access control: In a distributed database system, it is important to ensure that data is secure and that access to it is controlled. This involves implementing appropriate security measures and access control mechanisms to protect data from unauthorized access or modification.
7. Performance optimization: A distributed database system needs to be optimized for performance to ensure that it can handle large volumes of data and user requests. This may involve optimizing query processing algorithms, improving network performance, or tuning database parameters to improve performance.
8. System administration: System administration involves managing the distributed database system and ensuring that it is running smoothly. This may involve tasks such as monitoring system performance, backing up data, and resolving system issues.

Features:

Data partitioning: A distributed database system can partition data across multiple nodes or servers to improve scalability and performance.

Data replication: A distributed database system can replicate data across multiple nodes or servers to improve fault tolerance and availability.

Distributed query processing: A distributed database system can perform queries across multiple nodes or servers to improve performance and efficiency.

Distributed transaction processing: A distributed database system can support transactions that span multiple nodes or servers, while ensuring data consistency and integrity.

Consensus protocols: A distributed database system can use consensus protocols, such as Paxos or Raft, to ensure agreement and coordination among different nodes or servers.

Distributed locking mechanisms: A distributed database system can use distributed locking mechanisms, such as two-phase locking or timestamp ordering, to ensure data consistency and avoid conflicts.