RMAN Restore and Recovery - Oracle RMAN for Absolute Beginners - page 172

You can't perform an incomplete database recovery on a subset of your database's online data files. When
performing incomplete database recovery, all the checkpoint SCNs for all online data files must be synchronized
before you can open your database with the ALTER DATABASE OPEN RESETLOGS command. You can view the data file
header SCNs and the status of each data file via this SQL query:

select file#, status, fuzzy,
error, checkpoint_change#,
to_char(checkpoint_time,'dd-mon-rrrr hh24:mi:ss') as checkpoint_time
from v$datafile_header;

■ the FUZZY column V$DATAFILE_HEADER contains data files that have one or more blocks with an sCN value
greater than or equal to the checkpoint sCN in the data file header. If a data file is restored and has a FUZZY value of YES ,
then media recovery is required.

Note

The only exception to this rule of not performing an incomplete recovery on a subset of online database files is a
tablespace point-in-time recovery (TSPITR), which uses the RECOVER TABLESPACE UNTIL command. TSPITR is used
in rare situations; it restores and recovers only the tablespace(s) you specify. For more details on TSPITR, see RMAN
Recipes for Oracle Database 12c .
The recovery portion of an incomplete database recovery is always initiated with the RECOVER DATABASE UNTIL
command. RMAN will automatically recover your database up to the point specified with the UNTIL clause. Just like
the RESTORE command, you can recover up to time, change/SCN, log sequence number, or restore point. When RMAN
reaches the specified point, it will automatically terminate the recovery process.

■ regardless of what you specify in the UNTIL clause, rMaN will convert that into a corresponding UNTIL SCN
clause and assign the appropriate sCN. this is to avoid any timing issues, particularly those caused by daylight
saving time.

Note

During a recovery, RMAN will automatically determine how to apply redo. First, RMAN will apply any
incremental backups available. Next, any archived redo log files on disk will be applied. If the archived redo log files
do not exist on disk, then RMAN will attempt to retrieve them from a backup set. If you want to apply redo as part of
an incomplete database recovery, the following conditions must be true:

• Your database is in archivelog mode.

• You have a good backup of all data files.

• You have all redo required to restore up to the specified point.

■ starting with oracle 10g, you can perform parallel media recovery by using the RECOVER DATABASE PARALLEL
command.

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