Introduction

Distributed
database is defined as a database which can be stored on multiple computers. Today,
in the age of advances in Information Technology, there is important for people
to gain access of the updated information on hand. Users have the opportunity
to gain access of the information at anywhere and anytime in the network by
using the distributed database. The security issues and concurrency control in
distributed database are discussed in paper 1.

Theory

Based
on paper 1, the communication and data processing have been improved by using
the distributed database system. This is because the data on distributed
database is spread throughout different computer network sites. Not only for
increasing the speed of data access, but it also provides a local control of
data for users and a single-point of failure is much less probably to arise.
Distributed database is a database which is spread across multiple computers
that are connected via the data communication links. The advantage of
distributed database is data is distributed, so that the network traffic can be
reduced. Moreover, if the network of the company is temporarily broken, the
local database does not affected and it will remain the works. Due to the distributed
database is stored in multiple computers, so that the work of one branch will
not be affected when there is problems exist in other branch. However, to
ensure that the information and indexes are not altered will become more
difficult. Besides that, it is not well-organized when there is heavy
interactions occur between sites.

Literatures
review

Fragmentation,
replication and data allocation are presented as the design of distributed
database. According to the research of Shin and Irani 2, fragmentation is
defined as a design method which is used to divide the relation into two or
more partitions. Parallelism is one of the advantages of fragmentation. The
degree of concurrency and parallelism is increased due to the transaction can
be divided into several sub queries by using the fragmentation. However, the
overall performance and integrity control will become slow and difficult to
control due to the data are stored at different sites. Fragmentation is divided
into three types which is horizontal, vertical and hybrid fragmentation. Corolel
and Morris described that data replication is refer to the storage of data
copies at different locations and different sites that served by a computer
network 3. Maintain the stability of data is becoming the main problem in
managing the replicated data. There are several advantages of replication which
included improved response time, reduced the network traffic and also increased
the reliability and availability. The process of deciding where to locate the data
is known as the data allocation and the algorithm is considered into several
factors such as performance and data availability goals 4. Data allocation
strategies are classified into centralized data allocation, partitioned data
allocation and replicated data allocation.

Result outcome

According
to paper 1, it explained a lot of details about the concurrency control and
security in distributed database. Concurrency control in distributed database
is defined as the action of processing the concurrent access to the database. Distributed
two-phase locking (2PL) is the most familiar distributed concurrency control
system. “read any, write all” is the main approach of 2PL protocol and it is
used as the basic concurrency control protocol 5. Each transaction in 2PL have
executed in two phase which is growing phase and shrinking phase. Growing phase
is for obtains locks in transaction, while shrinking phase is for releases
locks. Lock managers in 2PL are spread to all sites and each of them is
responsible to lock the data at that site. Distributed Optimistic protocol is another
protocol for concurrency control. It is operated through exchange the certification
information. Security is important in distributed database. It is used to prevent
the information and data modified or misused by other people. In this paper,
there are four security components is presented which is security
authentication, authorization, encryption and also access control. Moreover,
deadlock is clarified as the major problem that occurs in distributed system.
In this research, 2PL algorithm with Timestamps mechanism is found that it is
effectively enough for concurrency control in distributed database.

Conclusion

In
paper 1, it is presented about the design, concurrency control and security
of distributed database. Security is one of the most important things in
distributed database as it is required to ensure that the information and data
is operating in a secure environment and integrity. Nowadays, distributed
database is becoming famous in computer science. Hence, we need to understand
it and try to find out the solutions to improve the weakness of the distributed
database.