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DAT 390 Wk 1 – Apply: Problem Set

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DAT 390 Wk 1 – Apply: Problem Set

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DAT 390 Wk 1 – Apply: Problem Set

DAT 390 Wk 1 – Apply: Problem Set

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.

  • True
  • False

 

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

  • All changes are aborted and returned to a previous consistent state.
  • The database is shut down for maintenance.
  • Five SQL statements are executed.
  • The end of a program is successfully reached.

 

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.

  • True
  • False

 

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.

  • common
  • unrelated
  • locked
  • shared

 

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

  • transaction
  • lock
  • database
  • schedule

 

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

  • lost updates
  • user errors
  • deadlocks
  • disk failures

 

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.

  • rollback manager
  • data dictionary
  • metadata
  • transaction log

 

In the optimistic approach, during the _____ phase, changes are permanently applied to the database.

  • read
  • write
  • validation
  • shared

 

_____ requires that all operations of a transaction be completed.

  • Time stamping
  • Atomicity
  • Durability
  • Specificity

 

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

  • unique
  • time stamping
  • scheduled
  • table-locking

 

The _____ isolation level ensures that queries return consistent results.

  • repeatable read
  • serializable
  • read committed
  • read uncommitted

 

What rule applies to the two-phase locking protocol?

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

 

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

  • diskblock
  • database table
  • database schema
  • disk sector

 

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

  • atomicity and isolation
  • serializability and isolation
  • atomicity and serializability
  • serializability and durability

 

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.

  • True
  • False

 

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

  • Isolation
  • Serializability
  • Atomicity
  • Time stamping

 

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

  • database-level
  • table-level
  • row-level
  • page-level

 

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.

  • True
  • False

 

A consistent database state is one in which all _____.

  • table are normalized
  • tables have foreign keys
  • SQL statements only update one table at a time
  • data integrity constraints are satisfied

 

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

  • True
  • False

 

The implicit beginning of a transaction is when _____.

  • the first SQL statement is encountered
  • the COMMIT command is issued
  • a database is started
  • a table is accessed for the first time

 

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

  • practical
  • time
  • physical
  • logical

 

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

  • True
  • False

 

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

  • ASSIGN
  • RETRIEVE
  • COMMIT
  • UPDATE

 

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

  • Stamps
  • Logs
  • Locks
  • Schedules

 

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

  • True
  • False

 

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.

  • validation
  • read
  • shared
  • write

 

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

  • True
  • False

 

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

  • True
  • False

 

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

  • exclusive lock
  • binary lock
  • shared lock
  • deadlock

 

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

  • True
  • False

 

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

  • binary lock
  • exclusive lock
  • deadlock
  • two-phase lock

 

In the wait/die scheme, the:

  • younger, preempted transaction is rescheduled using the same time stamp.
  • younger and older transactions both wait indefinitely to be release
  • older transaction waits for the younger one to complete and release its locks.
  • older transaction rolls back the younger transaction and reschedule it.

 

Lock _____ indicates the level of lock use.

  • granularity
  • shrinking
  • serializability
  • growing

 

A _____ lock will lock the entire diskpage.

  • table-level
  • transaction-level
  • page-level
  • row-level

 

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

  • growing
  • unlocking
  • locking
  • shrinking

 

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

  • Lost update problems
  • Inconsistent retrieval
  • Dirty read problems
  • The phenomena of uncommitted data

 

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

  • two-phase
  • binary
  • exclusive
  • shared

 

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

  • page-level
  • table-level
  • database table
  • row-level

 

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

  • True
  • False

 

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DAT 390 Wk 1 – Apply: Problem Set