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Exam 10: Transaction Management and Concurrency Control

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Question 21

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The _____ manager is responsible for assigning and policing the locks used by transactions.

A) transaction
B) database
C) lock
D) schedule

E) C) and D)
F) B) and C)

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Question 22

Multiple Choice

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In the wait/die scheme, the:

A) older transaction rolls back the younger transaction and reschedules it.
B) younger, preempted transaction is rescheduled using the same time stamp.
C) older transaction waits for the younger one to complete and release its locks.
D) younger and older transactions both wait indefinitely to be released.

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

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Question 23

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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) _____.

The serializable isolation level is the least restrictive level defined by the ANSI SQL standard.

The _____ occurs when two concurrent transactions, T1 and T2, are updating the same data element and one of the updates is lost.

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 semantically correct.

_____ occurs when a transaction accesses data before and after one or more other transactions finish working with such data.

What rule applies to the two-phase locking protocol?

_____ ensure that a disk physical failure will not impair the DBMS's ability to recover data.

The multiuser DBMS must implement controls to ensure serializability and isolation of transactions, in addition to atomicity and durability, in order to guard the database's consistency and integrity.

Transaction is a _____ unit of work that must be either entirely completed or aborted.

Of the following events, which is defined by ANSI as being equivalent to a ROLLBACK?

When using an optimistic approach, during the read phase, a transaction reads the database, executes the needed computations, and makes the updates to a private copy of the database values.

The DBMS uses the information stored in the _____log 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.

_____ are required to prevent another transaction form reading inconsistent data.

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

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.

Lock _____ indicates the level of lock use.

The _____ approach to scheduling concurrent transactions assigns a global unique stamp to each transaction.

What are database checkpoints?