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Distributed Databases : Question Paper May 2015 - Computer Engineering (Semester 6) | Mumbai University (MU)
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written 8.8 years ago by
teamques10
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Distributed Databases - May 2015
Computer Engineering (Semester 6)
TOTAL MARKS: 80
TOTAL TIME: 3 HOURS
(1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Assume data if required.
(4) Figures to the right indicate full marks.
1 Consider following global schema of a company database who keep track of company's employees, department and projects
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EMP
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ASG
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PROJ
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PAY
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i) Perform Primary Horizontal Fragmentation (PHF) of relation PROJ with pname and budget of projects given their number issued at three sites and access project information according to budget one site accesses ≤ 200000 other accesses>200000.
ii) Explain how the above resulting PHF fulfill the correctness rule of fragmentation.
iii) Perform Derive Horizontal Fragmentation (DHF) or relation EMP with respect to PAY (p1:sal>30000 and p2:sal≤30000).
iv) Explain how the above resulting DHF fulfill the correctness rules of fragmentation.(20 marks) 2 (a) Draw and explain model of transaction management inDDB.(10 marks) 2 (b) Explain Following transparency for distributed database.(10 marks) 3 (a) Draw and explain Layers of Query Processing in distributed database.(10 marks) 3 (b) What is query optimization? List distributed query optimization algorithms and explain any one from that.(10 marks) 4 (a) University database contains information about the course and the Professors who teach the courses in each semester. Each course must also have information about the number of student enrolled, room no. data and time (when and where the course is coupled)
i) Write DTD rules for above XML documents.
ii) Create an XML schema for above XML documents.(10 marks) 4 (b) Describe any two method for deadlock detection in distributed database?(10 marks) 5 (a) Explain Timestamp-based concurrency control mechanisms in DDB.(10 marks) 5 (b) State the purpose of 2PC protocol. Explain 2PC in detail.(10 marks)
Write short notes on (any two):
6 (a) Architecture of Heterogeneous database.(10 marks) 6 (b) Affinity Matrix(10 marks) 6 (c) Design issue of Distributed Database.(10 marks) 6 (d) Distributed Database Architecture.(10 marks)
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written 8.0 years ago by
naikpradnesh4
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2 (a) Draw and explain model of transaction management inDDB. Ans:Model for Transaction Management
In a Distributed System, Transactions are classified into two categories: Local Transactions & Global Transactions. If the data requirement of a transaction can be fulfilled from the local site, it is called as a Local Transaction. Local transactions access data only from local sites On the other hand, Transactions accessing data from remote site or multiple sites are called as Global Transactions. This complicated task is performed by four high level interconnected modules of the DBMS. These are Transaction Manager, Concurrency Control Manager, Recovery Manager, and Buffer Manager. Transaction Manager: It coordinates transaction on behalf of application programs by communicating with the scheduler and implements a particular strategy for concurrency control. Concurrency Control Manager: Its responsibility is to maximize concurrency, without allowing concurrently executing transactions to interfere with one another. thereby maintain consistency and isolation of transaction Recovery Manager: It preserves the database in a consistent state in case of failures Buffer Manager: It manages the efficient transfer of data between disk storage and main memory. In a distributed DBMS, all these modules exist in each local DBMS. In addition, a global transaction manager or transaction coordinator is required at each site to control the execution of global transactions as well as of local transactions initiated at that site. Therefore, an abstract model of transaction management at each site of distributed system consists of two different sub modules: the Transaction Manager and the Transaction Coordinator.
The Transaction Manager at each site manages the execution of the transactions that access data stored at that local site. Each such transaction may be local transaction or part of a global transaction. The structure of the transaction manager is similar to that of its counterpart in a centralized system. Each site has a local transaction manager responsible for: Maintaining a log for recovery purposes in each case of failure Participating in coordinating the concurrent execution of the transactions executing at that site.
The Transaction Coordinator at each site in a distributed system coordinates the execution of both local and global transactions initiated at that site. This component or module is not required in centralized DBMSs, as there is only one site in a centralized system. Each site has a transaction coordinator, which is responsible for: Starting the execution of transactions that originate at the site. Distributing sub transactions at appropriate sites for execution. Coordinating the termination of each transaction that originates at the site, which may result in the transaction being committed at all sites or aborted at all sites.
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