The document presents an overview of distributed databases and their management systems, highlighting characteristics, types (homogeneous and heterogeneous), and challenges such as resource distribution and data updating. It discusses advantages and disadvantages of using distributed database management systems, as well as problems encountered, solutions proposed, and future research directions in updating strategies. The conclusion emphasizes the necessity for ongoing assessments of challenges in distributed databases.

1. 12/16/20141

2. I’m:
Iftikhar Ahmad
Roll No: 13
From:
M-C-S (3rd sem)
AWKUM (shankar)2

3. Presentation Topic
Distributed Database & Issues + Challenges
 Homogeneous Database
 Heterogeneous Database
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4. Introduction:
A “Distributed Database”: is a logically interrelated collection
of shared data (and a description of this data), physically
distributed over a computer network.
A “Distributed DBMS” (DDBMS): is a Software system that
permits the management of the distributed database and
makes the distribution transparent to users.
Distributed Database
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5.  DDBMS has following characteristics:
o Collection of logically-related shared data.
o Data split into fragments.
o Sites linked by a communication network.
o Data at each site is under control of a DBMS.
o Each DBMS participates in at least one global application.
o Data sharing
o Data communication reliability and costs
o Database recovery
o Transaction and analytic processing
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Characteristics DDB

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Important difference between DDBMS and
distributed processing !
DDBMS Distributed processing of
centralised DBMS

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Why use a DDBMS? (!)
Advantages:
• Reflects organizational structure.
• Improved share ability.
• Improved availability.
• Improved reliability.
• Improved performance.
• Economics.
• Modular growth.
Disadvantages:
• Complexity.
• Cost.
• Security.
• Integrity control more difficult.
• Lack of standards.
• Lack of experience.
• Database design more complex.

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Types of Distributed Database System
DDBMS
Homogenous Heterogeneous
 Homogeneous
 Heterogeneous

9. The prefix “homo” – indicate sameness
 All sites use same DBMS product.
•
In this type of database has all data center have same
software.
Much easier to design and manage.
It appears to user as a single system.
Allows increased performance.
Much easier to design and manage.
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Homogeneous DB

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Same software
Homogeneous DB

11.  Advantages of Homogeneous DB:
 Easy to use
 Easy to mange
 Easy to Design
 Disadvantages of Homogeneous DB:
 Difficult for most organizations to force a homogeneous environment.
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12. The prefix “hetero” – indicate difference
 Sites may run different DBMS products, underlying data models.

 In this type of database , Different data center may run different
DBMS products.
 Occurs when sites have implemented their own databases and
integration is considered later.
• Translations required to allow for:
• Different hardware.
• Different DBMS products.
• Different hardware and DBMS products.
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Heterogeneous DB

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Sql oracle
Heterogeneous DB

14.  Advantages of Heterogeneous DB:
 Huge data can be stored in one Global center from different data
center.
 Remote access is done using the global schema.
 Different DBMSs may be used at each node.
 Disadvantages of Heterogeneous DB:
 Difficult to mange.
 Difficult to design. 12/16/201414

15.  Problems & their solutions:
The challenges encountered in distributed
database transaction and proffered likely solutions. Few
of the mentioned challenges are; problems of
distribution of resources, search and updating of
resources.
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Problems of Distributed Database
(Transactions)

16.  Distribution of resources problem:
This has to do with equal distribution of resources across
all servers. There are two approaches to solving this problem in a
distributed database environment; decentralize by function, or
decentralize by location.
(a) Decentralize by function: This works well with data that will be
accessed repeatedly by the same users. Example includes putting
manufacturing materials list at the appropriate manufacturing plants
and customer information at sales locations.
(b) Decentralize by location: Occurs when you partition customer
information on a node per region or other geographical based entity
within an organisation as seen in figure.
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18. Each telephone company independently implements the
common protocols by the international phone network,
e.g. for dialling and billing as shown in figure 2, the
dialling and billing of customer vary from one country to
another. The only centralize function is the architecture
of these protocols. It is worthy to note that design and
architecture are typically centralize within each
company; while operation and control are delegated to
the operating countries which in turn delegate operation
and maintenance to individuals responsible for
maintaining their own hardware and software.
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19.  SEARCHING:
Another notable problem of distributed database results
from lack of adequate knowledge of the entire database. For example, locating
where file x, y, z was stored. The solution to the challenge is using the concepts of
global & local data.
i. Global data involves information that is common to all sites and shared by all sites.
ii. Local data is information that is strictly meant for an individual site although it is
accessible to all sites.
Information is made available to the whole network by partitioning or replicating
the data files. Partitioning involves splitting a data file into records and then
distributing the records across networks while replication means duplicating
records at more than one location/node. Partitioning only works with local data
while global data are replicated.
Example
i. A typical example is found in bank transactions where servers are located in local
vicinity where customers can transact which often increases the speed of
transaction when traffics are eradicated.
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20. Advantages of partitioning a network:
i. It makes data available to all remote users
ii. It reduces traffics and increase speed of access
Advantages of replicating a network:
i. Replication improves data availability
ii. Replication improves response time.
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21.  UPDATING:
As discussed above, partitioning of
data is most efficient when the data are kept current that is,
updated regularly. The single copy of each data item makes
updating an efficient process. However. nonlocal “read”
operations are more expensive, making partitioning less
efficient for data that is widely used but updated infrequently.
Replicated data is most efficient when multiple reads of the
data are expected, but updates are not as regular compared to
partitioning process. The data is duplicated at nodes where
high- volume reads are expected, producing high availability and
good response time. When replicated data must be updated,
however, an update to a record at one node should cause an
identical update at all other nodes where that record resides. If
any one replica is unavailable there could be problems.
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22. A variety of schemes can be employed for updating Replicated
data, even though the copy of the record may be temporarily
unavailable at one or more of the nodes. One technique requires
that a majority of the replicas be read and updated as part of each
transaction, though the definition of “majority” varies with the
application. This scheme has the advantage of tolerating some
nodal unavailability, but it is not practical for either very small or
very large networks. In a very small network of, say, two nodes,
having either node unavailable prevents an update of a majority of
the nodes. In larger networks, delays in completing the update
transaction are proportional to network size: As the network
grows, transactions will take longer to complete.
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23.  Future work:
The studies on researching new update
strategies include the experimental distributed database
management system extension by the implementation of
the chosen update methods in the EDDBMS, work out of
the replicated data update method in the VSM
environment and its implementation. The next step will
concentrate on setting the assumptions on the use of this
algorithm in the other distributed programming
environments and on consideration of the possibility of
applying the system for building a data warehouse.
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24. The presentation has treated the proposed challenges
of distributed database system & basics. However, new
challenges show up daily in transactions. Therefore
there may be need for constant reviewers of these
challenges.
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CONCLUSION

25. Iftkr
iffi910
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