052-208(新增70题2018)

In which two cases would you perform only consistent backup? (Choose two.)

A. You are working on a database where downtime is not tolerated.

B. You are working on a database where downtime can be tolerated.

C. You are working on a database that operates in ARCHIVELOG mode.

D. You are working on a database that operates in NOARCHIVELOG mode.

E. You are working on a database where all the tablespaces are locally managed.

F. You are working on a database where control files and redo log files are multiplexed.

G. You are working on a database where control files and redo log files are not multiplexed.

Answer: BD
Consistent and Inconsistent Backups 

A backup is either consistent or inconsistent. To make a consistent backup, your database must have been shut down cleanly and remain closed for the duration of the backup. All committed changes in the online redo log files are written to the data files during the shut down process, so the data files are in a transaction-consistent state. When you restore your data files from a consistent backup, you can open the database immediately.

If the database is in ARCHIVELOG mode, then you can make inconsistent backups that are recoverable using archived redo log files. Open database backups are inconsistent because the online redo log files contain changes not yet applied to the data files. The online redo log files must be archived and then backed up with the data files to ensure recoverability.

consistent backup 

Assume that the database is open and you want to make a consistent backup of the whole database. This example shuts down the database consistently, mounts the database, makes a consistent whole database backup, and then opens the database.

SHUTDOWN IMMEDIATE;
STARTUP MOUNT;
BACKUP DATABASE PLUS ARCHIVELOG;
# Now that the backup is complete, open the database.
ALTER DATABASE OPEN;