1) Complexity:
Replication of data in a distributed database adds complexity to the DDBMS.
However, adequate data replication is necessary to achieve data availability
and reliability.
2) More Costly:
Increased complexity and a more extensive infrastructure means extra labour
costs. Distributed database systems require expert professionals with in-depth
knowledge to be developed, tested, and implemented. This requires high payment;
so they are more costly. In addition to software, a DDBMS requires additional
hardware to establish a network among the sites (database servers).
3) Security:
In a DDBMS, it is not only required to
control the access to replicated data
from multiple locations, but also to secure the network. Remote database
fragments must be secured, and they are not centralised so the remote sites
must be secured as well.
4) Difficult to Maintain Integrity: In a
DDBMS, the communication and processing costs that are required to enforce the
integrity constraints on databases are very high as the data is stored at
various physically separated sites.
5) Increased
Processing Overheads: In DDBMS exchange of data as messages and additional
computation to achieve the coordination among sites imposes a processing
overhead which does not arise in centralised systems.
6) Inexperience:
Distributed databases arc difficult to work with, and as a young there is not
much readily available experience on proper practice.
7) Lack of
Standards: There are no tools or methodologies yet to help users to convert
a centralised DBMS into a distributed DBMS.
8) Database
Design More Complex: Besides the normal difficulties, the design of a
distributed database has to consider fragmentation of data,, allocation of
fragments to specific sites and data replication.
9) Greater Potential for Bugs: Since the
sites of a distributed system operate concurrently, it is more difficult to
ensure the correctness of algorithms implemented in the program (software).
