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Exam 10: Transaction Management and Concurrency Control

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Question 31

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A(n) ____ condition occurs when two or more transactions wait for each other to unlock data.

A) deadlock
B) exclusive lock
C) binary lock
D) two-phase lock

E) A) and B)
F) A) and D)

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Question 32

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The information stored in the ____ is used by the DBMS for a recovery requirement triggered by a ROLLBACK statement,a program's abnormal termination,or a system failure such as a network discrepancy or a disk crash.

A) data dictionary
B) metadata
C) rollback manager
D) transaction log

E) A) and B)
F) A) and C)

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Question 33

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A consistent database is ____.

A ____ lock locks the entire table preventing access to any row by a transaction while another transaction is using the table.

The phenomenon of uncommitted data occurs when two transactions are executed concurrently and the first transaction is rolled back after the second transaction has already accessed the uncommitted data-thus violating the isolation property of transactions.

A diskpage,or page,is the equivalent of a ____.

The objective of ____________________ control is to ensure the serializability of transactions in a multiuser database environment.

What is transaction isolation and why it is important?

____________________ control is important because the simultaneous execution of transactions over a shared database can create several data integrity and consistency problems.

All transactions must display ____.

If a(n)____________________ is issued before the termination of a transaction,the DBMS will restore the database only for that particular transaction,rather than for all transactions,in order to maintain the durability of the previous transactions.

If T1 has not unlocked data item Y,T2 cannot begin;if T2 has not unlocked data item X,T1 cannot continue.Consequently,T1 and T2 each wait for the other to unlock the required data item.Such a deadlock is also known as a(n)____________________.

Most real-world database transactions are formed by only one database request.

The DBMS keeps several copies of ____________________ to ensure that a disk physical failure will not impair the DBMS's ability to recover data.

ANSI defines four events that signal the end of a transaction.Of the following events,which is defined by ANSI as being equivalent to a COMMIT?

Although the DBMS is designed to recover a database to a previous consistent state (when an interruption prevents the completion of a required set of transactions),the transactions themselves are defined by the end user or programmer and must be ____________________ correct.

____________________-level locks are less restrictive than database-level locks,but they create traffic jams when many transactions are waiting to access the same table.

The implicit beginning of a transaction is ____.

A(n) ____ lock exists when concurrent transactions are granted read access on the basis of a common lock.

A(n) ____ specifically reserves access to the transaction that locked the object.