Disadvantages of Distributed DBMS

Distributed Database Systems is a kind of DBMS where databases are present at different locations and connected via a network. Each site in a Distributed Database is capable of accessing and processing local data as well as remote data. Although, distributed DBMS is capable of effective communication and data sharing still it suffers from various disadvantages are as following below. 

1. Complex nature : 
   Distributed Databases are a network of many computers present at different locations and they provide an outstanding level of performance, availability, and of course reliability. Therefore, the nature of Distributed DBMS is comparatively more complex than a centralized DBMS. Complex software is required for Distributed DBMS. Also, It ensures no data replication, which adds even more complexity in its nature. 
    
2. Overall Cost : 
   Various costs such as maintenance cost, procurement cost, hardware cost, network/communication costs, labor costs, etc, adds up to the overall cost and make it costlier than normal DBMS. 
    
3. Security issues: 
   In a Distributed Database, along with maintaining no data redundancy, the security of data as well as a network is a prime concern. A network can be easily attacked for data theft and misuse. 
    
4. Integrity Control: 
   In a vast Distributed database system, maintaining data consistency is important. All changes made to data at one site must be reflected on all the sites. The communication and processing cost is high in Distributed DBMS in order to enforce the integrity of data. 
    
5. Lacking Standards: 
   Although it provides effective communication and data sharing, still there are no standard rules and protocols to convert a centralized DBMS to a large Distributed DBMS. Lack of standards decreases the potential of Distributed DBMS.
6. Lack of Professional Support:
   Due to a lack of adequate communication standards, it is not possible to link different equipment produced by different vendors into a smoothly functioning network. Thus several good resources may not be available to the users of the network.
7. Data design complex:  
   Designing a distributed database is more complex compared to a centralized database. 
    

If the data is not properly distributed at different sites, then the query processing time will increase and response to requests will become slow.