Page 171 - DCAP402_DCAO204_DATABASE MANAGEMENT SYSTEM_MANAGING DATABASE

Database Management Systems/Managing Database

Notes 9.17 Self Assessment

Fill in the blanks:
1. Database ............................ are the units in which programs read or write information.
2. Once the DBMS informs the user that a transaction has been successfully completed, its
effects should persist even if the system crashes before all its changes are reflected on disk
known as .................................
3. ................................... is the initial state of a transaction.
4. .................................. state occurs after the discovery that normal execution can no longer
proceed.
5. Transaction-processing systems usually allow multiple transactions to run concurrently
(at the same time) known as ....................................
6. Users are responsible for ensuring transaction ...................................
7. The .......................... locking protocol ensures serializability.
8. .............................. protocols ensure that the system will never enter into a deadlock state.
9. When a deadlock is detected, some transaction will have to be rolled back to break the
........................................
10. A transaction is an execution of a user program and is seen by the DBMS as a
................................. or list of actions.

9.18 Review Questions

1. What are the properties of transaction? Explain briefly.

2. Write short notes on transactions and schedules.
3. Explain lock-based concurrency control in detail.
4. What are ACID properties? Explain.
5. Why we need concurrent execution of transactions?

6. Describe the strict two-phase locking (strict 2PL) protocol.
7. What transaction characteristics are under programmer control in SQL? Discuss various
access modes and isolation levels.

8. Explain transaction state in detail.
9. Describe concurrent execution. Also explain motivation for concurrent execution.
10. Explain Thomas Write Rule.

Answers: Self Assessment

1. ‘objects’ 2. durability

3. Active state 4. Failed
5. concurrent execution of transactions 6. consistency
7. two-phase 8. Deadlock prevention
9. deadlock 10. series

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