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