題目：

193.What is the purpose of the recover command? (Choose all that apply.)
A. Recover database datafiles from physical disk backup sets.
B. Recover required incremental backups from physical disk backup sets.
C. Recover required archived redo logs from physical disk backup sets.
D. Apply incremental backups to recover the database.
E. Apply archived redo logs to recover the database.
?
參考答案 BCDE
解析
題目意思問，recover命令的目的是什么？
選項A，說的是命令restore。

參考文檔：

https://docs.oracle.com/cd/E11882_01/backup.112/e10643/rcmsynta2001.htm#RCMRF140

RECOVER

Purpose

Use the RECOVER command to perform one of the following distinct tasks:

• Perform complete recovery of the whole database or one or more restored data files

• Perform point-in-time recovery of a database (DBPITR) or tablespace (TSPITR)

• Apply incremental backups to a data file image copy (not a restored data file) to roll it forward in time

• Recover a corrupt data block or set of data blocks within a data file

See Also:

Oracle Database Backup and Recovery User's Guide to learn how to recover data files

Prerequisites

All redo or incremental changes required for the recovery must exist on disk or in SBT. If RMAN needs to restore incremental backups or archived redo log files during recovery, then you must either have automatic channels configured or manually allocate channels of the same type that created these backups.

If you perform media recovery on an encrypted tablespace, then the Oracle wallet must be open when performing media recovery of this tablespace. See Oracle Database Administrator's Guide to learn about encrypted tablespaces.

Prerequisites Specific to RECOVER BLOCK

The following prerequisites apply to RECOVER BLOCK:

• The target database must run in ARCHIVELOG mode and be open or mounted with a current control file.

• RMAN can only recover blocks marked media corrupt. The V$DATABASE_BLOCK_CORRUPTION view indicates which blocks in a file were marked corrupt since the most recent BACKUP or BACKUP ... VALIDATE command was run against the file.

• The backups of the data files containing the corrupt blocks must be full backups and not proxy backups. If only proxy backups exist, then you can restore them to a nondefault location on disk, in which case RMAN considers them data file copies. You can then use the data file copies for block media recovery.

• RMAN can use only archived redo log files for recovery. Block media recovery cannot survive a missing or inaccessible log, although it can sometimes survive missing or inaccessible records (see Oracle Database Backup and Recovery User's Guide).

• For RMAN to be able to search the flashback logs for good copies of corrupt blocks, Flashback Database must be enabled on the target database.

• For RMAN to be able to search a standby database for good copies of corrupt blocks, the target database must be associated with a physical standby database in a Data Guard environment. In addition, the physical standby database must be open read-only in managed recovery.

Note:

An active Data Guard license is required for this operation.

Usage Notes

By default, RMAN performs complete recovery. For point-in-time recovery, the best practice is to enter a SET UNTIL command before both the RESTORE and RECOVER commands in a RUN command so that the UNTIL time applies to both commands. If you run SET UNTIL after restoring the database, then you may not be able to recover the database to the target time because the restored files may have timestamps later than the target time.

Note:

You must open the database with the RESETLOGS option after incomplete recovery or recovery with a backup control file.

Incremental Backups and Archived Redo Log Files

Except for RECOVER BLOCK, RMAN can use both incremental backups and archived redo log files for recovery. RMAN uses the following search order:

Incremental backup sets on disk or tape

Archived redo log files on disk

Archived redo log backups on disk

Archived redo log backup sets on tape

When RMAN chooses a destination to restore archived redo log files, it uses the following order of precedence:

SET ARCHIVELOG DESTINATION

The LOG_ARCHIVE_DEST_n parameter whose value is set to LOCATION=USE_DB_RECOVERY_FILE_DEST

LOG_ARCHIVE_DEST_1

RMAN can apply incremental backups to data files that were not restored from an incremental backup. If overlapping levels of incremental backup exist, then RMAN automatically chooses the level covering the longest period of time.

END

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