DBMS Materials

Unknown    

Distributed database as a collection of multiple,logically interrelated databases distributed over a computer network.

A distributed database management system (distributed DBMS) is then defined as the software system that permits the management of the distributed database and makes the distribution transparent to the users.

Distributed database systems (DDBS) are systems that have their data distributed and replicated over several locations; unlike the centralized data base system (CDBS), where one copy of the data is stored.


Data may be replicated over a network using horizontal and vertical fragmentation similar to projection and selection operations in Structured Query Language (SQL).Both types of database share the same problems of access control and transaction management, such as user concurrent access control and deadlock detection and resolution. On the other hand, however, 
Database is interconnected data.There is set of operation to access data.DBMS contains enterprizes database.DBMS application in different field banking,airline,university,etc.There is problem to store data is space need.There is more data, if we need to delete it then whole data deleted,we need thus data change status active to disable.Thus,it have more storage are possibles.

Drawback of the system is failure of update records.


I provides different DBMS materials provides.Click below link for download materials.The Materials helpful in the Gate Exam As well as in placement exam.There are different basic concept as well as query question.

Advantages of Distributed DBS:
Ø  Since organizations tend to be geographically dispersed, a DDBS fits the organizational structure better than traditional centralized DBS.
Ø  Each location will have its local data as well as the ability to get needed data from other locations via a communication network.
Ø  Moreover, the failure of one of the servers at one site won’t render the distributed database system inaccessible. The affected site will be the only one directly involved with that failed server.
Ø  If any data is required from a site exhibiting a failure, such data may be retrieved from other locations containing the replicated data. The performance of the system will improve, since several machines take care of distributing the load of the CPU and the I/O.
Ø  Also, the expansion of the distributed system is relatively easy, since adding a new location doesn’t affect the existing ones.

Disadvantages of Distributed DBS :
On the other hand, DDBS has several disadvantages.
Ø  A distributed system usually exhibits more complexity and cost more than a centralized one.
Ø  This is true because the hardware and software involved need to maintain a reliable and an efficient system.
Ø  All the replication and data retrieval from all sites should be transparent to the user.
Ø  The cost of maintaining the system is considerable since technicians and experts are required at every site.
Ø  Another main disadvantage of distributed database systems is the issue of security.
Ø  Handling security across several locations is more complicated.

v Example:-

Here we take GOOGLE Data server as Distributed  Database.

v Google data center locations
v If you include data centers that are under construction, Google has 19 locations in the US where they operate data centers, 12 in Europe, one in Russia, one in South America, and three in Asia. Not all of the locations are dedicated Google data centers, since they sometimes lease space in other companies’ data centers.