My dear students of Database Management Class (BE11),
Below is the list of questions you need to answer. Each of you must answer a question (only one question) in the comment field. Anyone can choose a question to answer. Questions that have been chosen and answered by someone else can not be chosen and answered twice. In other words, you can only choose and answer a question that is still free. Thus a student will correspond exactly with a question. Only good answers will be rewarded 10 points for your final exam. The deadline is sunday, 17th May 2015.
List of questoins:
1. Explain why data replication is important and needed.
2. Find and identify the benefits of using replication in a distributed system.
3. Give examples of typical applications that use replication
4. Compare and contrast eager with lazy replication
5. Describe the CAP theorem
6. Compare and contrast the different types of data ownership models available in the replication environment. Provide an example for each model.
7. Describe different ways of implementing a replication architecture
8. Describe the functionality required of mobile DBMS.
9. Describe how mobile database support the mobile worker.
Thank you.
This comment has been removed by the author.
ReplyDeleteGood evening sir,
ReplyDeletehere my answer of question number 2 about the benefit of using replication in distributed system.
Sugianto - 1601259123
Benefit of using replication in distributed system
- Availability
replication is increase the availability of data for user and application through the provision of alternatives data access options. example is if one site is unavailable, the user can continue to query or even update using the another location.
- Reliability
multiple copies of data provides excellent recovery in the event of failure at one or more sites.
- Performance/ load reduction
improving a performance by diving a tasks to all replication it can help the main system to lower their load.
- Disconnected computing
By using replication the user can work on a subset of corporate database while disconnected from a main database server. when connection is re-established, user can synchronize data(replica) with the corporate database.
-Support many user
Replication can create multiple customized replica that meet the requirements of each user or group of users of the system.
- Support advanced application
Replication can help to support advanced application like OLAP or data mining. furthermore, through replication the corporate data can also be made available to support the increasingly popular trend of mobile computing.
Good evening,
ReplyDeleteI'm going to answer the number 2 question about data replication.
Data replication is important because it's preventing a major data loss. If data are the most important things to a company, than a major data loss is not acceptable. If the company have a data backup, making a backup data into a working database may take a lot of efforts. By using data replications it can be prevented. Because networks of databases is keeping curent data accross location.
Replication of data is needed to reduced data redudancies. If a data loss happened backup data may not run and can be use immediately. In data replication a network of copied databases can take over seamlessly. The seamless nature of data replication, is reducing data redudancies. In data backup, the backedup data can be over a day old or hours, depending on the amount of transactions this can cause a loss of a lot of money or material.
Have a nice weekend,
Fagra Hanif
Sorry sir I meant number 1 question, about why data replication is important and needed.
DeleteGood evening sir,
ReplyDeletehere my answer of question number 5. Describe the CAP theorem
Aendy Suwarno - 1601226283
A database can provide strong consistency and system availability during network partitions. The common belief that this combination is impossible is based on a misunderstanding of the CAP theorem.(Eric Bayer)
From what I get in
http://nosqlguide.com/nosql-patterns/cap-theorem-what-does-it-mean-to-you/
1. C(Consistency). All parts of the computer system see the same data at the same time
2. A(Availability). Every request made to the system receives a response, whether positive or negative
3. P(Partition tolerance.) The system still functions even if with message loss or partial failure
From what I read in that link
CAP theorem is for seeing the same data in the same time, receiving the response and function able whether it lost message or partial failure in all the system so the database is strong and always available during the partition
In CAP itself it can be combine with just 2 word itself:
• CA (Consistency and Availability): relational database management systems (RDBMS)
• CP (Consistency and Partition Tolerance): MongoDB document store and Redis key-value store
• AP (Availability and Partition Tolerance): Couch DB document store and Riak key-value store
However, further consideration shows that CA is not really a coherent option because a system that is not Partition-tolerant will, by definition, be forced to give up Consistency or Availability during a partition.
Good Evening Sir,
ReplyDeleteHere's my answer to the following question.
Question :
9. Describe how mobile database support the mobile worker.
Answer :
Based on my understanding about mobile DBMS, i think mobile database is considered as a feature that allows us the users to operate the database whenever and wherever we want to. It is not something that is crucially important to the business in many ways, but it is something to improve the quality of our database management and also something that will increase our company's performance.
With the use of this mobile database, users don't always have to go their computers to open and see the database, they can easily access it through their smatphones and such. It is very good for the mobility we need it the modern world.
A family of mine is one of the good examples when it comes about mobile database. He is one of the IT officer in the company, and he needs to check the company's database every once in a while to make sure everything is going as it is. With such requirement, he needs to find a way to make the database accessible whenever and wherever he is. And to make this possible, this mobile database comes and works just as he desired and it helps him a lot during the off days of work. He could just download the database files into his smartphone, and boom! he can open it anytime anywhere without any needs of internet connection or computer.
Based on this explanation, i think the mobile database is considered as the solution for the mobile workers to improve their quality to the company.
I hope this answers accurately,
Thank you.
Hardian Ikhsan
1601247483
Database Management
This comment has been removed by the author.
ReplyDeleteGood evening sir,
ReplyDeleteThis is my answer for number 8 question - Describe the functionality required of mobile DBMS.
Steven - 1601230356
Answer:
• Communicate with the centralized database server through modes such as wireless or Internet access;
• Replicate data on the centralized database server and mobile device;
• Synchronize data on the centralized database server and mobile device;
• Capture data from various sources such as the Internet;
• Manage data on the mobile device;
• Analyze data on a mobile device;
• Create customized mobile applications.
Good evening sir this is my answer to number 4 :
ReplyDeleteIvandiwira - 1601258890
there are two methods of replication; eager replication
(synchronous) and lazy replication (asynchronous). Eager replication provides excellent
data consistency by synchronizing transactions prior to commitment, but does so at the
expense of performance. Eager replication is known for deadlocking, its inability to scale
well, and excessive communications overhead. Deadlocking is most often the
result of multi-site commit protocols such as two-phase commit, that block until all nodes
have committed a transaction. Lazy replication or asynchronous replication is known
for high scalability and performance, but low data consistency due to the fact that
asynchronous transactions are not ACID (Atomicity, Consistency, Isolation, Durability)
compliant and therefore fail to meet the consistency requirement . ACID compliance,
while assuring high levels of data consistency, traditionally has not provided high
availability, which in most cases takes precedence over consistency in most user-centric
applications where stale data or approximated data is sufficient.