OCA-11-Managing Data Concurrency and Undo

Pregunta 1 de 20

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1. Changes made with an UPDATE statement in a transaction are permanent in the data-base and visible to other users after what occurs?

Selecciona una o más de las siguientes respuestas posibles:

A. DBWR flushes the changes to disk.
B. You issue a SAVEPOINT statement.
C. You issue a COMMIT statement.
D. A checkpoint occurs.

Explicación

Pregunta 2 de 20

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2. Which of the following commands returns an error if the transaction starts with SET
TRANSACTION READ ONLY ?

Selecciona una o más de las siguientes respuestas posibles:

A. ALTER SYSTEM
B. SET ROLE
C. ALTER USER
D. None of the above

Explicación

Pregunta 3 de 20

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3. Guaranteed undo retention can be specified for which of the following objects?

Selecciona una o más de las siguientes respuestas posibles:

A. A tablespace
B. A table
C. The database
D. A transaction
E. The instance

Explicación

Pregunta 4 de 20

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4. Which of the following lock modes permits concurrent queries on a table but prohibits
updates to the locked table?

Selecciona una o más de las siguientes respuestas posibles:

A. ROW SHARE
B. ROW EXCLUSIVE
C. SHARE ROW EXCLUSIVE
D. All of the above

Explicación

Pregunta 5 de 20

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5. Select the statement that is not true regarding undo tablespaces.

Selecciona una o más de las siguientes respuestas posibles:

A. Undo tablespaces will not be created if they are not specified in the CREATE
DATABASE command.
B. Two undo tablespaces can be active if a new undo tablespace was specified and the
old one contains pending transactions.
C. You can switch from one undo tablespace to another while the database is online.
D. UNDO_MANAGEMENT cannot be changed dynamically while the instance is running.

Explicación

Pregunta 6 de 20

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6. To resolve a lock conflict, which of the following methods can you use? Choose all
that apply.

Selecciona una o más de las siguientes respuestas posibles:

A. Oracle automatically resolves the lock after a short but predefined time period by
killing the session that is holding the lock.
B. The DBA can kill the session holding the lock.
C. The user can either roll back or commit the transaction that is holding the lock.
D. Oracle automatically resolves the lock after a short but predefined period by killing
the session that is requesting the lock.

Explicación

Pregunta 7 de 20

1

7. Two transactions occur at the wall clock times in the following table. What happens
at 10:05?

Selecciona una o más de las siguientes respuestas posibles:

A. Session 2 will wait for session 1 to commit or roll back.
B. Session 1 will wait for session 2 to commit or roll back.
C. A deadlock will occur, and both sessions will hang unless one of the users cancels
their statement or the DBA kills one of the sessions.
D. A deadlock will occur, and Oracle will cancel one of the statements.
E. Neither session is updating the same column, so no waiting or deadlock will occur.

Explicación

Pregunta 8 de 20

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8. If all extents in an undo segment fill up, which of the following occurs next? Choose
all that apply.

Selecciona una o más de las siguientes respuestas posibles:

A. A new extent is allocated in the undo segment if all existing extents still contain
active transaction data.
B. Other transactions using the segment are moved to another existing segment with
enough free space.
C. A new undo segment is created, and the transaction that filled up the undo segment
is moved in its entirety to another undo segment.
D. The first extent in the segment is reused if the undo data in the first extent is
not needed.
E. The transaction that filled up the undo segment spills over to another undo segment.

Explicación

Pregunta 9 de 20

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9. Which of the following commands returns control to the user immediately if a table is
already locked by another user?

Selecciona una o más de las siguientes respuestas posibles:

A. LOCK TABLE HR.EMPLOYEES IN EXCLUSIVE MODE WAIT DEFERRED;
B. LOCK TABLE HR.EMPLOYEES IN SHARE MODE NOWAIT;
C. LOCK TABLE HR.EMPLOYEES IN SHARE MODE WAIT DISABLED;
D. LOCK TABLE HR.EMPLOYEES IN EXCLUSIVE MODE NOWAIT DEFERRED;

Explicación

Pregunta 10 de 20

1

10. Undo information falls into all the following categories except for which one?

Selecciona una o más de las siguientes respuestas posibles:

A. Uncommitted undo information
B. Undo information required in case an instance crash requires a roll forward
operation when the instance is restarted
C. Committed undo information required to satisfy the undo retention interval
D. Expired undo information that is no longer needed to support a running transaction

Explicación

Pregunta 11 de 20

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11. Undo segments are owned by which user?

Selecciona una o más de las siguientes respuestas posibles:

A. SYSTEM
B. The user who initiated the transaction
C. SYS
D. The user who owns the object changed by the transaction

Explicación

Pregunta 12 de 20

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12. The EM Database Express Undo Advisor uses what to recommend the new size of the
undo tablespace?

Selecciona una o más de las siguientes respuestas posibles:

A. The value of the parameter UNDO_RETENTION
B. The number of Snapshot too old errors
C. The current size of the undo tablespace
D. The desired amount of time to retain undo data
E. The most recent undo generation rate

Explicación

Pregunta 13 de 20

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13. Choose the option that is true regarding locks in Oracle Database 12c.

Selecciona una o más de las siguientes respuestas posibles:

A. When session 1 has a table locked using the LOCK TABLE...EXCLUSIVE MODE statement,
all DML statements and queries wait until session 1 does a COMMIT or ROLLBACK .
B. When SELECT...FOR UPDATE is performed, the table is locked.
C. The DDL_LOCK_TIMEOUT parameter can be set to TRUE to not return the
ORA-00054 error.
D. The LOCK TABLE statement can include the WAIT clause to specify the number of
seconds to wait for acquiring the lock.

Explicación

Pregunta 14 de 20

1

14. The following table shows the timestamp and actions by two users. Choose the best
option that describes the outcome of the actions.

Selecciona una o más de las siguientes respuestas posibles:

A. John’s query will return the same results all three times it is executed as they are
run in the same session.
B. John’s queries run at 10:16 and 10:20 produce the same result, which is different
from the one at 10:14.
C. John’s query run at 10:16 waits until 10:18 to produce results, waiting for the com-
mit to happen.
D. John’s queries run at 10:14 and 10:16 produce the same result, which is different
from the one at 10:20.

Explicación

Pregunta 15 de 20

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15. Which statement is true regarding the locking behavior of Oracle Database 12c?

Selecciona una o más de las siguientes respuestas posibles:

A. Readers block writers.
B. Writers block readers.
C. Readers block writers.
D. Writers do not block readers.

Explicación

Pregunta 16 de 20

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16. Identify the operation that does not generate redo.

Selecciona una o más de las siguientes respuestas posibles:

A. An INSERT statement reading from a global temporary table into a persistent table
B. An INSERT statement reading from a persistent table into a global temporary table
C. Roll back an UPDATE operation
D. Writing undo records during a DML operation

Explicación

Pregunta 17 de 20

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17. User Maria just called to let you know that the long-running query she runs every
week just received a Snapshot Too Old error. What is the best action you can take?

Selecciona una o más de las siguientes respuestas posibles:

A. Tell Maria to rerun the query.
B. Increase Undo Retention.
C. The materialized view used in the query is stale and needs to be refreshed.
D. Increase the undo tablespace size.

Explicación

Pregunta 18 de 20

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18. Which two statements regarding undo and transactions are true?

Selecciona una o más de las siguientes respuestas posibles:

A. Multiple active transactions can write concurrently to the same extent in an
undo segment.
B. Multiple active transactions can write concurrently to the same undo segment.
C. Each transaction acquires an extent in the undo segment and does not share
the extent.
D. Each transaction acquires a segment in the undo tablespace and does not share
the segments.

Explicación

Pregunta 19 de 20

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19. Which statement ends a transaction?

Selecciona una o más de las siguientes respuestas posibles:

A. UPDATE
B. ALTER TABLE
C. ALTER SESSION
D. ALTER SYSTEM

Explicación

Pregunta 20 de 20

1

20. Which statement regarding lock is true?

Selecciona una o más de las siguientes respuestas posibles:

A. A developer must lock the row before performing an update to prevent others from
changing the same row.
B. When a row in a table is locked, the table is locked and no other transactions can
update the table.
C. When two sessions try to update the same row at the same time, both sessions fail.
D. When a session tries to update the row already updated by another session, it waits
until the other session does a commit or rollback.

	Creado por Jamonero Blanco hace casi 8 años

OCA OCA Test sobre OCA-11-Managing Data Concurrency and Undo, creado por Jamonero Blanco el 29/01/2017.

OCA-11-Managing Data Concurrency and Undo

Pregunta 1 de 20

1. Changes made with an UPDATE statement in a transaction are permanent in the data-base and visible to other users after what occurs?

Selecciona una o más de las siguientes respuestas posibles:

Explicación

Pregunta 2 de 20

2. Which of the following commands returns an error if the transaction starts with SET TRANSACTION READ ONLY ?

Selecciona una o más de las siguientes respuestas posibles:

Explicación

Pregunta 3 de 20

3. Guaranteed undo retention can be specified for which of the following objects?

Selecciona una o más de las siguientes respuestas posibles:

Explicación

Pregunta 4 de 20

4. Which of the following lock modes permits concurrent queries on a table but prohibits updates to the locked table?

Selecciona una o más de las siguientes respuestas posibles:

Explicación

Pregunta 5 de 20

5. Select the statement that is not true regarding undo tablespaces.

Selecciona una o más de las siguientes respuestas posibles:

Explicación

Pregunta 6 de 20

6. To resolve a lock conflict, which of the following methods can you use? Choose all that apply.

Selecciona una o más de las siguientes respuestas posibles:

Explicación

Pregunta 7 de 20

7. Two transactions occur at the wall clock times in the following table. What happens at 10:05?

Selecciona una o más de las siguientes respuestas posibles:

Explicación

Pregunta 8 de 20

8. If all extents in an undo segment fill up, which of the following occurs next? Choose all that apply.

Selecciona una o más de las siguientes respuestas posibles:

Explicación

Pregunta 9 de 20

9. Which of the following commands returns control to the user immediately if a table is already locked by another user?

Selecciona una o más de las siguientes respuestas posibles:

Explicación

Pregunta 10 de 20

10. Undo information falls into all the following categories except for which one?

Selecciona una o más de las siguientes respuestas posibles:

Explicación

Pregunta 11 de 20

11. Undo segments are owned by which user?

Selecciona una o más de las siguientes respuestas posibles:

Explicación

Pregunta 12 de 20

12. The EM Database Express Undo Advisor uses what to recommend the new size of the undo tablespace?

Selecciona una o más de las siguientes respuestas posibles:

Explicación

Pregunta 13 de 20

13. Choose the option that is true regarding locks in Oracle Database 12c.

Selecciona una o más de las siguientes respuestas posibles:

Explicación

Pregunta 14 de 20

14. The following table shows the timestamp and actions by two users. Choose the best option that describes the outcome of the actions.

Selecciona una o más de las siguientes respuestas posibles:

Explicación

Pregunta 15 de 20

15. Which statement is true regarding the locking behavior of Oracle Database 12c?

Selecciona una o más de las siguientes respuestas posibles:

Explicación

Pregunta 16 de 20

16. Identify the operation that does not generate redo.

Selecciona una o más de las siguientes respuestas posibles:

Explicación

Pregunta 17 de 20

17. User Maria just called to let you know that the long-running query she runs every week just received a Snapshot Too Old error. What is the best action you can take?

Selecciona una o más de las siguientes respuestas posibles:

Explicación

Pregunta 18 de 20

18. Which two statements regarding undo and transactions are true?

Selecciona una o más de las siguientes respuestas posibles:

Explicación

Pregunta 19 de 20

19. Which statement ends a transaction?

Selecciona una o más de las siguientes respuestas posibles:

Explicación

Pregunta 20 de 20

20. Which statement regarding lock is true?

2. Which of the following commands returns an error if the transaction starts with SET
TRANSACTION READ ONLY ?

4. Which of the following lock modes permits concurrent queries on a table but prohibits
updates to the locked table?

6. To resolve a lock conflict, which of the following methods can you use? Choose all
that apply.

7. Two transactions occur at the wall clock times in the following table. What happens
at 10:05?

8. If all extents in an undo segment fill up, which of the following occurs next? Choose
all that apply.

9. Which of the following commands returns control to the user immediately if a table is
already locked by another user?

12. The EM Database Express Undo Advisor uses what to recommend the new size of the
undo tablespace?

14. The following table shows the timestamp and actions by two users. Choose the best
option that describes the outcome of the actions.

17. User Maria just called to let you know that the long-running query she runs every
week just received a Snapshot Too Old error. What is the best action you can take?