Q&A Hero

Humanities

Q: What are the three basic techniques to control deadlocks?
Q: How does a shared/exclusive lock schema increase the lock manager's overhead?
Q: Explain the transaction log. What is its function?
Q: What is transaction isolation and why it is important?
Q: Database transaction ____________________ restores a database from an inconsistent state to a previously consistent state.
Q: The DBMS keeps several copies of ____________________ to ensure that a disk physical failure will not impair the DBMS's ability to recover data.
Q: Uniqueness ensures that no equal time stamp values can exist, and ____________________ ensures that time stamp values always increase.
Q: 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) ____________________.
Q: The ____________________ rule states that only one transaction at a time can own an exclusive lock on the same object.
Q: As a rule, a(n) ____________________ must unlock the object after its termination.
Q: ____________________-level locks are less restrictive than database-level locks, but they create traffic jams when many transactions are waiting to access the same table.
Q: ____________________ can take place at any of the following levels: database, table, page, row, or field.
Q: Most multiuser ______________________________ automatically initiate and enforce locking procedures, where all locking information is managed by the lock manager.
Q: To determine the appropriate order of the operations, the scheduler bases its actions on concurrency control algorithms, such as ____________________ or time stamping methods.
Q: The ____________________ interleaves the execution of database operations to ensure serializability.
Q: ____________________ control is important because the simultaneous execution of transactions over a shared database can create several data integrity and consistency problems.
Q: The objective of ____________________ control is to ensure the serializability of transactions in a multiuser database environment.
Q: 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.
Q: 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.
Q: In the optimistic approach, during the ____ phase, changes are permanently applied to the database.a. read b. validation c. writed. shared
Q: 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. writed. shared
Q: The ____ approach to scheduling concurrent transactions assigns a global unique stamp to each transaction.a. scheduled b. table-locking c. uniqued. timestamping
Q: A(n) ____ condition occurs when two or more transactions wait for each other to unlock data.a. deadlock b. exclusive lock c. binary lockd. two-phase lock
Q: 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. lockingd. unlocking
Q: 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.
Q: A(n) ____ lock exists when concurrent transactions are granted read access on the basis of a common lock.a. shared b. exclusive c. binaryd. two-phase
Q: A(n) ____ specifically reserves access to the transaction that locked the object.a. shared lock b. exclusive lock c. binary lockd. deadlock
Q: A(n) ____ lock has only two stages (0 and 1).a. shared b. exclusive c. binaryd. two-phase
Q: A ____ lock allows concurrent transactions to access different rows of the same table.a. database-level b. table-level c. page-leveld. row-level
Q: A diskpage, or page, is the equivalent of a ____.a. database table b. disk sector c. database schemad. diskblock
Q: A ____ lock locks the entire diskpage.a. transaction-level b. table-level c. page-leveld. row-level
Q: 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-leveld. row-level
Q: Lock ____ indicates the level of lock use.a. granularity b. shrinking c. growingd. serializability
Q: The ____ manager is responsible for assigning and policing the locks used by the transactions.a. transaction b. database c. lockd. schedule
Q: ____ are required to prevent another transaction from reading inconsistent data.a. Locks b. Schedules c. Stampsd. Logs
Q: A ____ lock prevents the use of any tables in the database from one transaction while another transaction is being processed.a. database-level b. table-level c. page-leveld. row-level
Q: 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. unrelatedd. locked
Q: One of the three most common data integrity and consistency problems is ____.a. lost updates b. disk failures c. user errorsd. deadlocks
Q: 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 managerd. transaction log
Q: 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
Q: 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.
Q: 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.
Q: 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. UPDATEd. COMMIT
Q: 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 isolationd. atomicity and serializability
Q: All transactions must display ____. a. atomicity, consistency, and durability b. durability and isolation c. consistency, durability, and isolation d. atomicity, durability, consistency, and isolation
Q: ____ 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. Isolationd. Time stamping
Q: ____ requires that all operations of a transaction be completed.a. Specificity b. Atomicity c. Durabilityd. Time stamping
Q: 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
Q: A transaction is a ____ unit of work that must be either entirely completed or aborted.a. timed b. practical c. logicald. physical
Q: The last step in the write-through technique recovery procedure is to identify the last checkpoint in the transaction log.
Q: The transaction recovery write-ahead-log protocol ensures that transaction logs are always written before any database data are actually updated.
Q: When using an optimistic approach, during the write phase, the transaction is validated to ensure that the changes made will not affect the integrity and consistency of the database.
Q: An optimistic approach is based on the assumption that the majority of the database operations do not conflict.
Q: When using an optimistic approach, a transaction reads the database, executes the needed computations, and makes the updates to a private copy of the database values.
Q: A growing phase in a two-phase lock is when a transaction acquires all the required locks without locking any data.
Q: 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.
Q: A shared lock produces no conflict as long as all the concurrent transactions are read-write only.
Q: In a page-level lock, the DBMS will lock an entire diskpage.
Q: The scheduler establishes the order in which the operations within concurrent transactions are executed.
Q: The phenomenon of uncommitted dataoccurs when two transactions are executed concurrently and the first transaction is rolled back after the second transaction has already accessed the uncommitted datathus violating the isolation property of transactions.
Q: 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.
Q: 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.
Q: Incomplete or improper transactions can have a devastating effect on database integrity.
Q: Serializability means that data used during the execution of a transaction cannot be used by a second transaction until the first one is completed.
Q: Atomicity indicates the permanence of the database's consistent state.
Q: The DBMS guarantees that the semantic meaning of a transaction truly represents the real-world event.
Q: 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.
Q: To ensure consistency of the database, every transaction must begin with the database in an unstable state.
Q: Most real-world database transactions are formed by only one database request.
Q: At the level of middle management, the database must be able to ____. a. represent and support the company operations as closely as possible b. deliver the data necessary for tactical decisions and planning c. produce query results within specified performance levels d. provide access to external and internal data to identify growth opportunities and to chart the direction of such growth
Q: A DBMS facilitates ____. a. interpretation and presentation of data in useful formats b. destruction of data and information to the right people at the right time c. data presentation and data usage monitoring for adequate periods of time d. automatic auditing of all data changes
Q: The DBA can use an audit log to automatically record a brief description of the database operations performed by the users.
Q: Database access can be controlled by placing limits on the use of the DBMS's query and reporting tools.
Q: The DBA must define data views to protect and control the scope of the data that are accessible to an authorized user.
Q: Protecting the data in the database is a function of authorization management.
Q: Security breaches can yield a database whose integrity is either preserved or corrupted.
Q: The maintenance activities of the DBA are an extension of the operational activities.
Q: Training people to use the DBMS and its tools is not included in the DBA's technical activities.
Q: The allocation of storage resources is determined when the DBMS is created.
Q: System support activities cover all tasks directly related to the day-to-day operations of a DBMS and its applications.
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