Deck 10: Transaction Management and Concurrency Control

Question 1

In a page-level lock,the DBMS will lock an entire diskpage.

Answer 1

True

Question 2

A scheduler facilitates data isolation to ensure that two transactions do not update the same data element at the same time.

Answer 2

True

Question 3

Incomplete or improper transactions can have a devastating effect on database integrity.

Answer 3

True

Question 4

A lock guarantees the open use of a data item to multiple transactions.

Question 5

Timestamps must only have the single property of uniqueness.

Question 6

A shared lock produces no conflict as long as all the concurrent transactions are read-write only.

Question 7

Time stamping demands a lot of system resources because many transactions might have to be stopped,rescheduled,and stamped.

Question 8

The scheduler establishes the order in which the operations within concurrent transactions are executed.

Question 9

Durability requires that all portions of the transaction must be treated as a single,logical unit of work in which all operations are applied and completed to produce a consistent database.

Question 10

Atomicity indicates the permanence of the database's consistent state.

Question 11

Serializability means that data used during the execution of a transaction cannot be used by a second transaction until the first one is completed.

Question 12

A growing phase in a two-phase lock is when a transaction acquires all the required locks without locking any data.

Question 13

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

Question 14

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.

Question 15

The DBMS guarantees that the semantic meaning of a transaction truly represents the real-world event.

Question 16

An optimistic approach is based on the assumption that the majority of the database operations do not conflict.

Question 17

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.

Question 18

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.

Question 19

A field-level lock allows concurrent transactions to access the same row,as long as they require the use of different fields within that row.

Question 20

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.

Question 21

requires that all operations of a transaction be completed.

A)Specificity
B)Atomicity
C)Durability
D)Time stamping

Question 22

means that data used during the execution of a transaction cannot be used by a second transaction until the first one is completed.

A)Serializability
B)Atomicity
C)Isolation
D)Time stamping

Question 23

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 ROLLBACK?

A)Five SQL statements are executed.
B)The end of a program is successfully reached.
C)The program is abnormally terminated.
D)The database is shut down for maintenance.

Question 24

The ANSI has defined standards that govern SQL database transactions.Transaction support is provided by two SQL statements: and ROLLBACK.

A)RETRIEVE
B)ASSIGN
C)UPDATE
D)COMMIT

Question 25

A transaction is a unit of work that must be either entirely completed or aborted.

A)timed
B)practical
C)logical
D)physical

Question 26

The reason for the different levels of isolation is to increase transaction concurrency.

Question 27

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

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

Question 28

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

Question 29

A single-user database system automatically ensures of the database,because only one transaction is executed at a time.

A)serializability and durability
B)atomicity and isolation
C)serializability and isolation
D)atomicity and serializability

Question 30

The last step in the write-through technique recovery procedure is to identify the last checkpoint in the transaction log.

Question 31

are required to prevent another transaction from reading inconsistent data.

A)Locks
B)Schedules
C)Stamps
D)Logs

Question 32

As long as two transactions,T1 and T2,access data,there is no conflict,and the order of execution is irrelevant to the final outcome.

A)shared
B)common
C)unrelated
D)locked

Question 33

The transaction recovery write-ahead-log protocol ensures that transaction logs are always written before any database data are actually updated.

Question 34

Lock indicates the level of lock use.

A)granularity
B)shrinking
C)growing
D)serializability

Question 35

A consistent database state is .

A)one in which all tables have foreign keys
B)one in which all data integrity constraints are satisfied
C)one in which all tables are normalized
D)one in which all SQL statements only update one table at a time

Question 36

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

A)Inconsistent retrievals
B)The phenomena of uncommitted data
C)Lost update problems
D)Dirty read problems

Question 37

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

Question 38

One of the three most common data integrity and consistency problems is .

A)lost updates
B)disk failures
C)user errors
D)deadlocks

Question 39

The implicit beginning of a transaction is .

A)when the database is started
B)when a table is accessed for the first time
C)when the first SQL statement is encountered
D)when the COMMIT command is issued

Question 40

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?

A)Five SQL statements are executed.
B)The end of a program is successfully reached.
C)The program is abnormally terminated.
D)The database is shut down for maintenance.

Question 41

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

A)database table
B)disk sector
C)database schema
D)diskblock

Question 42

A lock allows concurrent transactions to access different rows of the same table.

A)database-level
B)table-level
C)page-level
D)row-level

Question 43

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

Question 44

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

A)shared lock
B)exclusive lock
C)binary lock
D)deadlock

Question 45

The scheduler's main job is to create a(n)of a transaction's operation,in which the interleaved executions of transactions yield the same results as if the transactions were executed in serial order.

Question 46

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

A)scheduled
B)table-locking
C)unique
D)timestamping

Question 47

What is a rule that applies to the two-phase locking protocol?

A)Two transactions cannot have conflicting locks.
B)No unlock operation can precede a lock operation in a different transaction.
C)No data is affected until all locks are released.
D)No data is affected until the transaction is in its locked position.

Question 48

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

Question 49

A lock locks the entire diskpage.

A)transaction-level
B)table-level
C)page-level
D)row-level

Question 50

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

Question 51

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.

Question 52

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

A)database-level
B)table-level
C)page-level
D)row-level

Question 53

In the wait/die scheme,:

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

Question 54

A(n)phase in a two-phase lock is when a transaction releases all locks and cannot obtain any new lock.

A)growing
B)shrinking
C)locking
D)unlocking

Question 55

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.

Question 56

A(n)occurs when a transaction executes a query at time t1,and then it runs the same query at time t2,yielding additional rows that satisfy the query.

A)phantom read
B)dirty read
C)uncommitted dependency
D)nonrepeatable read

Question 57

The isolation level ensures that queries return consistent results.
a.Read Uncommitted
b.Read Committed
c.Serializable
d.Repeatable Read

Question 58

In the optimistic approach,during the phase,a transaction scans the database,executes the needed computations,and makes the updates to a private copy of the database values.

A)read
B)validation
C)write
D)shared

Question 59

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

A)shared
B)exclusive
C)binary
D)two-phase

Question 60

In the optimistic approach,during the phase,changes are permanently applied to the database.
a.read
b.validation
c.write
d.shared

Question 61

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

Question 62

What is transaction isolation and why it is important?

Question 63

The interleaves the execution of database operations to ensure serializability.

Question 64

What are database checkpoints?

Question 65

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

Question 66

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)_____.

Question 67

Uniqueness ensures that no equal time stamp values can exist,and ensures that time stamp values always increase.

Question 68

can take place at any of the following levels: database,table,page,row,or field.

Question 69

Database transaction restores a database from an inconsistent state to a previously consistent state.

Question 70

To determine the appropriate order of the operations,the scheduler bases its actions on concurrency control algorithms,such as or time stamping methods.

Question 71

Explain the transaction log.What is its function?

Question 72

Most multiuser automatically initiate and enforce locking procedures,where all locking information is managed by the lock manager.

Question 73

In a heavily used database management system (DBMS),the prevention and detection of constitutes an important DBMS function.

Question 74

How does a shared/exclusive lock schema increase the lock manager's overhead?

Question 75

The rule states that only one transaction at a time can own an exclusive lock on the same object.

Question 76

As a rule,a(n)must unlock the object after its termination.