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- OCA Oracle 12C Administration(1Z0-062)
31.
Changes made with an UPDATE statement in a transaction are permanent in the database
and visible to other users after what occurs?
- A.DBWR flushes the changes to disk.
- B.You issue a SAVEPOINT statement.
- C.You issue a COMMIT statement.
- D.A checkpoint occurs.
- Answer & Explanation
- Report
Answer : [C]
Explanation :
Explanation :
| By ending the transaction, a commit makes pending DML changes permanent. A rollback also ends the transaction. When a checkpoint occurs, DBWR flushes dirty buffers to disk, which is independent of transaction boundaries. |
32.
Which of the following commands returns an error if the transaction starts with SET
TRANSACTION READ ONLY?
- A.ALTER SYSTEM
- B.SET ROLE
- C.ALTER USER
- D.None of the above
- Answer & Explanation
- Report
Answer : [D]
Explanation :
Explanation :
| When you use SET TRANSACTION READ ONLY, no data changes can be made in the transaction. You can make DDL changes though. A DDL statement does an implicit COMMIT and ends the transaction. ALTER USER is a DDL statement. |
33.
Guaranteed undo retention can be specified for which of the following objects?
- A.A tablespace
- B.A table
- C.The database
- D.A transaction
- E.The instance
- Answer & Explanation
- Report
Answer : [A]
Explanation :
Explanation :
| Guaranteed undo retention can be set at the tablespace level by using the RETENTION GUARANTEE clause with either the CREATE TABLESPACE or ALTER TABLESPACE command. Only undo tablespaces can have this attribute. |
34.
Which of the following lock modes permits concurrent queries on a table but prohibits
updates to the locked table?
- A.ROW SHARE
- B.ROW EXCLUSIVE
- C.SHARE ROW EXCLUSIVE
- D.All of the above
- Answer & Explanation
- Report
Answer : [C]
Explanation :
Explanation :
| SHARE ROW EXCLUSIVE mode permits concurrent queries but prohibits updates to the locked table. SHARE mode is required to create an index on the table. ROW SHARE is the least restrictive mode of the table lock and allows updates on the table. ROW EXCLUSIVE locks the modified rows, but allows updates to the table for nonlocked rows. SHARE lock held by a transaction allows other transactions to query the rows, but updates are allowed when a single transaction holds the share table lock. |
35.
Select the statement that is not true regarding undo tablespaces.
- 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.
- Answer & Explanation
- Report
Answer : [A]
Explanation :
Explanation :
| If an undo tablespace is not explicitly created in the CREATE DATABASE command, Oracle automatically creates one with the name SYS_UNDOTBS. |
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