Deck 9: Managing Multiuser Databases

Question 1

Locks placed automatically by the DBMS are called implicit locks.

Answer 1

True

Question 2

A transaction is a group of alternative database actions,from which the database can choose to perform only one of them.

Answer 2

False

Question 3

In general,the overall responsibility of the DBA is to facilitate the development and use of the database system.

Answer 3

True

Question 4

Explicit locks are locks that are placed automatically by the DBMS.

Question 5

Database administration tasks have to be performed for single-user,personal databases.

Question 6

Changes in the database structure usually involve only one application.

Question 7

An exclusive lock locks the item from change but not from read access.

Question 8

Locks with large granularity are easy for the DBMS to administer but frequently cause conflicts.

Question 9

Locks placed by a command issued to the DBMS from the application program are called explicit locks.

Question 10

An exclusive lock locks the item from access of any type.

Question 11

Database administration is more important but less difficult in multiuser database systems than in single-user database systems.

Question 12

The size of a lock is referred to as the lock granularity.

Question 13

The DBA has to find a balance between the conflicting goals of maximizing availability of the database to users and protecting the database.

Question 14

Concurrency control measures are taken to ensure that one user's work has absolutely no influence on another user's work.

Question 15

Resource locking is one remedy to the lost update problem.

Question 16

One important reason for documenting changes to the database structure is for diagnosing errors.

Question 17

The database is most vulnerable to failure after a change to its structure.

Question 18

A transaction is sometimes called atomic because it is performed as a unit.

Question 19

The DBA is responsible for managing changes to the database structure,but is rarely involved in the original design of the structure.

Question 20

A transaction is a series of actions to be taken on the database such that either all of them are performed successfully or none of them is performed at all.

Question 21

The transaction boundaries are the essential information that the DBMS needs from the application programs to enforce different locking strategies.

Question 22

In general,optimistic locking is the preferred technique for Internet databases.

Question 23

Resource locking must be carefully planned because most DBMS products cannot detect a deadlock condition.

Question 24

Resources are locked for a shorter amount of time with pessimistic locking because the transaction is pre-processed.

Question 25

Two-phased locking has a growing phase and a shrinking phase.

Question 26

A static cursor processes a snapshot of the relation that was taken when the cursor was opened.

Question 27

Repeatable Read isolation is the most restrictive level of isolation.

Question 28

In two-phase locking,all locks are obtained during the growing phase.

Question 29

Nonrepeatable reads occur when a transaction rereads data it has previously read and finds modifications or deletions caused by a committed transaction.

Question 30

The goal of database security is to ensure that only authorized users can perform authorized activities at authorized times.

Question 31

Transaction level consistency means that all rows impacted by any actions in a transaction are protected from change during the entire transaction.

Question 32

A dynamic cursor saves primary key values when the cursor is opened and retrieves the values for each row as the application program accesses it.

Question 33

With optimistic locking,the assumption is made that no conflict will occur.

Question 34

A dirty read happens when one transaction reads a changed record that has not been committed to the database.

Question 35

In two-phase locking,all locks are released during the contracting phase.

Question 36

A durable transaction is one for which all committed changes are permanent.

Question 37

Two-phased locking is a scheme for achieving serializability of transactions.

Question 38

According to ANSI SQL,the serializable isolation level will not allow phantom reads,dirty reads,and nonrepeatable reads.

Question 39

Requiring all application programs to lock resources in the same order is one way of preventing a deadlock condition.

Question 40

With pessimistic locking,the assumption is made that a conflict will occur.

Question 41

Processing responsibilities should be documented and encoded into manual procedures.

Question 42

Rollforward is a method of database recovery that restores the database save and all valid transactions since the save was reapplied.

Question 43

All commercial DBMS products use some version of "username and password" as part of their security features.

Question 44

Which of the following is not a database administration responsibility of a DBA?

A)Managing the database structure
B)Writing the applications
C)Managing the DBMS
D)Maintaining the data repository

Question 45

Which of the following is true about making changes to the database structure?

A)The DBA need not get input from users on the issue because it is a technical decision.
B)Formal policies and procedures for requesting a change are not used because they are too limiting.
C)Documentation of when the change was made,how it was made,and why it was made must be created.
D)Changes do not produce unexpected results because the DBA will have investigated the change thoroughly before implementing it.

Question 46

Both rollforward and rollback require the use of a log of transaction results.

Question 47

A standby data repository is one which requires a person to generate the metadata and place it in the repository.

Question 48

A database save is used to mark the end of a transaction.

Question 49

A checkpoint is a point of synchronization between the database and the transaction log.

Question 50

The security provided by the DBMS often has to be augmented by additional security features within the application program.

Question 51

An active data repository is one in which the metadata is automatically created as the system components are created.

Question 52

In regard to database security,neither the DBMS nor the database applications can enforce processing responsibilities.

Question 53

Reprocessing is normally the most convenient method for recovery after a system failure.

Question 54

Copies of each database record or page before being changed by a transaction that are saved for use in database recovery are called before images.

Question 55

The DBA should periodically analyze run-time statistics of database performance to help manage the DBMS.

Question 56

Rollforward and reprocessing are two different names for the same technique.

Question 57

Processing rights may be implemented at the DBMS level.

Question 58

To support rollforward and rollback recovery,transactions must be written to a script before they are applied to the database.

Question 59

A passive data repository is preferred over an active repository because it requires less human intervention.

Question 60

Copies of each database record or page after it was changed by a transaction that are saved for use in database recovery are called ghost images.

Question 61

When two transactions are being processed against the database at the same time ________.

A)they are called concurrent transactions
B)they are usually interleaved
C)they always result in a lost update problem
D)Both A and B are correct

Question 62

Which of the following is true of forward only cursors?

A)Current values for each row are retrieved when the application accesses a row.
B)All changes of any type from any source are visible.
C)Changes made by the transaction are visible only if they occur on rows ahead of the cursor.
D)It requires the greatest overhead of any cursor type.

Question 63

Measures that are taken to prevent one user's work from inappropriately influencing another user's work are called ________.

A)concurrency control
B)checkpoint
C)database recovery
D)database logging

Question 64

Which of the following is not true about two-phased locking?

A)Cannot obtain a new lock once a lock has been released
B)Uses only shared locks
C)Has a growing phase
D)Has a shrinking phase

Question 65

The situation that occurs when one user's changes to the database are lost by a second user's changes to the database is known as the ________.

A)lost update problem
B)deadly embrace problem
C)inconsistent read problem
D)inconsistent write problem

Question 66

When a transaction reads a row that has been changed,but the change has not been committed,this is known as a ________.

A)Clean read
B)Dirty read
C)Nonrepeatable read
D)Phantom read

Question 67

Which type of lock still allows other transactions to have read-only access to the locked resource?

A)Exclusive lock
B)Shared lock
C)Explicit lock
D)Implicit lock

Question 68

A lock placed automatically by the DBMS is called a(n)________ lock.

A)exclusive
B)explicit
C)shared
D)implicit

Question 69

Which of the following is allowed by "Repeatable Read Isolation"?

A)Nonrepeatable reads
B)Dirty reads
C)Phantom reads
D)Both A and B are correct

Question 70

Requiring all application programs to lock resources in the same order is a technique for preventing what problem?

A)Concurrent update
B)Lost update
C)Deadlock
D)Exclusive locks

Question 71

One remedy for the inconsistencies caused by concurrent processing is ________.

A)concurrency
B)checkpointing
C)rollback
D)resource locking

Question 72

Locks that are placed assuming that a conflict will occur are called ________.

A)explicit locks
B)implicit locks
C)optimistic locks
D)pessimistic locks

Question 73

Which type of lock prevents all types of access to the locked resource?

A)Exclusive lock
B)Shared lock
C)Explicit lock
D)Implicit lock

Question 74

A series of actions to be taken on the database such that either all actions are completed successfully,or none of them can be completed,is known as a ________.

A)checkpoint
B)log
C)lock
D)transaction

Question 75

When a transaction rereads data that has been changed and finds changes due to committed transactions,this is known as a ________.

A)Clean read
B)Dirty read
C)Nonrepeatable read
D)Phantom read

Question 76

Which of the following is not true about locks?

A)Locks with large granularity are easier for the DBMS to administer.
B)Locks with small granularity cause more conflicts.
C)Locks may have a database-level granularity.
D)Locks may have a table-level granularity.

Question 77

Locks that are placed assuming that a conflict will not occur are called ________.

A)dynamic
B)shared
C)pessimistic
D)optimistic

Question 78

The situation that occurs when two users are each waiting for a resource that the other person has locked is known as a(n)________.

A)lost update problem
B)deadlock
C)inconsistent read problem
D)checkpoint

Question 79

Ensuring that all rows impacted by the actions of a transaction are protected from changes until the entire transaction is completed is called ________.

A)statement level consistency
B)optimistic locking
C)transaction level consistency
D)durable transactions

Question 80

The task of diagnosing errors due to changes in the database structure is eased by ________.

A)formal policies for requesting changes
B)database structure change documentation
C)rollback analysis
D)configuration control