8446333
Descripción
Test por Miguel Lucero, actualizado hace más de 1 año
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Creado por Miguel Lucero
hace más de 7 años
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Pregunta 1
Pregunta
1. Most real-world database transactions are formed by only one database request.
Respuesta
- True
- False
Pregunta 2
Pregunta
2. 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.
Respuesta
- True
- False
Pregunta 3
Pregunta
3. The DBMS guarantees that the semantic meaning of a transaction truly represents the real-world event.
Respuesta
- True
- False
Pregunta 4
Pregunta
4. Atomicity indicates the permanence of the database's consistent state.
Respuesta
- True
- False
Pregunta 5
Pregunta
5. Serializability means that data used during the execution of a transaction cannot be used by a second transaction until the first one is completed.
Respuesta
- True
- False
Pregunta 6
Pregunta
6. Incomplete or improper transactions can have a devastating effect on database integrity.
Respuesta
- True
- False
Pregunta 7
Pregunta
7. 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.
Respuesta
- True
- False
Pregunta 8
Pregunta
8. 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.
Respuesta
- True
- False
Pregunta 9
Pregunta
9. 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.
Respuesta
- True
- False
Pregunta 10
Pregunta
10. The scheduler establishes the order in which the operations within concurrent transactions are executed.
Respuesta
- True
- False
Pregunta 11
Pregunta
11. A scheduler facilitates data isolation to ensure that two transactions do not update the same data element at the same time.
Respuesta
- True
- False
Pregunta 12
Pregunta
12. A lock guarantees the open use of a data item to multiple transactions.
Respuesta
- True
- False
Pregunta 13
Pregunta
13. In a page-level lock, the DBMS will lock an entire diskpage.
Respuesta
- True
- False
Pregunta 14
Pregunta
14. 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.
Respuesta
- True
- False
Pregunta 15
Pregunta
15. A shared lock produces no conflict as long as all the concurrent transactions are read-write only.
Respuesta
- True
- False
Pregunta 16
Pregunta
16. A growing phase in a two-phase lock is when a transaction acquires all the required locks without locking any data.
Respuesta
- True
- False
Pregunta 17
Pregunta
17. Timestamps must only have the single property of uniqueness.
Respuesta
- True
- False
Pregunta 18
Pregunta
18. Time stamping demands a lot of system resources because many transactions might have to be stopped, rescheduled, and stamped.
Respuesta
- True
- False
Pregunta 19
Pregunta
19. An optimistic approach is based on the assumption that the majority of the database operations do not conflict.
Respuesta
- True
- False
Pregunta 20
Pregunta
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.
Respuesta
- True
- False
Pregunta 21
Pregunta
21. The serializable isolation level is the least restrictive level defined by the ANSI SQL standard.
Respuesta
- True
- False
Pregunta 22
Pregunta
22. The reason for the different levels of isolation is to increase transaction concurrency.
Respuesta
- True
- False
Pregunta 23
Pregunta
23. The transaction recovery write-ahead-log protocol ensures that transaction logs are always written before any database data are actually updated.
Respuesta
- True
- False
Pregunta 24
Pregunta
24. The last step in the write-through technique recovery procedure is to identify the last checkpoint in the transaction log.
Respuesta
- True
- False
Pregunta 25
Pregunta
25. A transaction is a unit of work that must be either entirely completed or aborted.
Respuesta
-
a. timed
-
b. practical
-
c. logical
-
d. physical
Pregunta 26
Pregunta
26. A consistent database state is .
Respuesta
-
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
Pregunta 27
Pregunta
27. requires that all operations of a transaction be completed.
Respuesta
-
a. Specificity
-
b. Atomicity
-
c. Durability
-
d. Time stamping
Pregunta 28
Pregunta
28. means that data used during the execution of a transaction cannot be used by a second transaction until the first one is completed.
Respuesta
-
a. Serializability
-
b. Atomicity
-
c. Isolation
-
d. Time stamping
Pregunta 29
Pregunta
29. A single-user database system automatically ensures of the database, because only one transaction is executed at a time.
Respuesta
-
a. serializability and durability
-
b. atomicity and isolation
-
c. serializability and isolation
-
d. atomicity and serializability
Pregunta 30
Pregunta
30. The ANSI has defined standards that govern SQL database transactions. Transaction support is provided by two SQL statements: and ROLLBACK
Respuesta
-
a. RETRIEVE
-
b. ASSIGN
-
c. UPDATE
-
d. COMMIT
Pregunta 31
Pregunta
31. 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?
Respuesta
-
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.
Pregunta 32
Pregunta
32. 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?
Respuesta
-
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.
Pregunta 33
Pregunta
33. The implicit beginning of a transaction is .
Respuesta
-
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
Pregunta 34
Pregunta
34. 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.
Respuesta
-
a. data dictionary
-
b. metadata
-
c. rollback manager
-
d. transaction log
Pregunta 35
Pregunta
35. One of the three most common data integrity and consistency problems is .
Respuesta
-
a. lost updates
-
b. disk failures
-
c. user errors
-
d. deadlocks
Pregunta 36
Pregunta
36. occurs when a transaction accesses data before and after one or more other transactions finish working with such data.
Respuesta
-
a. Inconsistent retrievals
-
b. The phenomena of uncommitted data
-
c. Lost update problems
-
d. Dirty read problems
Pregunta 37
Pregunta
37. 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.
Respuesta
-
a. shared
-
b. common
-
c. unrelated
-
d. locked
Pregunta 38
Pregunta
38. are required to prevent another transaction from reading inconsistent data.
Respuesta
-
a. Locks
-
b. Schedules
-
c. Stamps
-
d. Logs
Pregunta 39
Pregunta
39. The______ manager is responsible for assigning and policing the locks used by the transactions.
Respuesta
-
a. transaction
-
b. database
-
c. lock
-
d. schedule
Pregunta 40
Pregunta
40. Lock indicates the level of lock use.
Respuesta
-
a. granularity
-
b. shrinking
-
c. growing
-
d. serializability
Pregunta 41
Pregunta
41. A lock locks the entire table preventing access to any row by a transaction while another transaction is using the table.
Respuesta
-
a. database-level
-
b. table-level
-
c. page-level
-
d. row-level
Pregunta 42
Pregunta
42. A lock locks the entire diskpage.
Respuesta
-
a. transaction-level
-
b. table-level
-
c. page-level
-
d. row-level
Pregunta 43
Pregunta
43. A diskpage, or page, is the equivalent of a .
Respuesta
-
a. database table
-
b. disk sector
-
c. database schema
-
d. diskblock
Pregunta 44
Pregunta
44. A lock allows concurrent transactions to access different rows of the same table.
Respuesta
-
a. database-level
-
b. table-level
-
c. page-level
-
d. row-level
Pregunta 45
Pregunta
45. A(n) specifically reserves access to the transaction that locked the object.
Respuesta
-
a. shared lock
-
b. exclusive lock
-
c. binary lock
-
d. deadlock
Pregunta 46
Pregunta
46. A(n) lock exists when concurrent transactions are granted read access on the basis of a common lock
Respuesta
-
a. shared
-
b. exclusive
-
c. binary
-
d. two-phase
Pregunta 47
Pregunta
47. What is a rule that applies to the two-phase locking protocol?
Respuesta
-
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
Pregunta 48
Pregunta
48. A(n) phase in a two-phase lock is when a transaction releases all locks and cannot obtain any new lock.
Respuesta
-
a. growing
-
b. shrinking
-
c. locking
-
d. unlocking
Pregunta 49
Pregunta
49. A(n) condition occurs when two or more transactions wait for each other to unlock data.
Respuesta
-
a. deadlock
-
b. exclusive lock
-
c. binary lock
-
d. two-phase lock
Pregunta 50
Pregunta
50. The approach to scheduling concurrent transactions assigns a global unique stamp to each transaction.
Respuesta
-
a. scheduled
-
b. table-locking
-
c. unique
-
d. timestamping
Pregunta 51
Pregunta
51. In the wait/die scheme,:
Respuesta
-
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.
Pregunta 52
Pregunta
52. 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.
Respuesta
-
a. read
-
b. validation
-
c. write
-
d. shared
Pregunta 53
Pregunta
53. In the optimistic approach, during the phase, changes are permanently applied to the database.
Respuesta
-
a. read
-
b. validation
-
c. write
-
d. shared
Pregunta 54
Pregunta
54. The isolation level ensures that queries return consistent results.
Respuesta
-
a. Read Uncommitted
-
b. Read Committed
-
c. Serializable
-
d. Repeatable Read
Pregunta 55
Pregunta
55. 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.
Respuesta
-
a. phantom read
-
b. dirty read
-
c. uncommitted dependency
-
d. nonrepeatable read
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