An engineering research community comprises a group of researchers stationed in
ID: 3855022 • Letter: A
Question
An engineering research community comprises a group of researchers stationed in different universities across Malaysia. This community uses a distributed system with a strong feature in database replications and disk storage replications.
Discuss,
a) Why is it necessary for this community to have such a strong feature in its distributed system? [10]
b) What is the major difference between these replications? [5]
Explanation / Answer
a) Since the team of researchers are stationed in different universities across malaysia, so that means all the individual researchers must be storing the data in their respective computers. The computers cannot be attached to a common processor but still the community members have to share and store the information among themselves in such a way that they can access the data relevant to their tasks without interfering with the work of others.
So, in order to share and store the information the community uses distributed database system. In a distributed system the storage devices are not attached to a common processor.The data may be stored in multiple computers located in the same physical location or it may be scattered over a network of interconnected computers.
A distributed system can reside on organised network servers or independent decentralised individual computers on the internet, on corporate intranets or extranets or on other organisation networks.
Distributed database is of two types:
To ensure that the distributed database remains up-to-date and current, a process called as REPLICATION is used.
Replication uses specialized software that looks for changes in the distributed database.After identifying the changes the replication process makes all the databases look the same. The replication process can be complex and time consuming depending on the size and number of distributed database.
b) Database replication: Database replication can be used in many database management systems mostly with the master /slave relationship between the original data and the copies of the data. The master allows the updation of the data, which moves through the slaves, the slaves then output a message that it has received the update successfully, thus sending subsequent updates.
When data is replicated between database servers, so that information remains consistent throughout the database system and user are not able to tell or know that they are using which server , the system is then said to exhibit replication transparency.
Disk Storage Replication: Real time disk storage replication takes place by distributing updates of a block device to several physical hard disks. This way any file supported by the operating system can be replicated without modification.A replication is extendable across a computer network, so , the disks can be located in physically distant locations. The purpose of replication is to prevent the damage from failures or disasters that may occur in one location.