Performing Incomplete Recovery - RMAN Recipes for Oracle Database 12c - page 363

For the majority of incomplete database recovery circumstances, you'll use the restore database until
command to instruct RMAN to retrieve data files from the RMAN backup files. This type of incomplete database
recovery is the main focus of this chapter. The until portion of the restore database command instructs RMAN to
retrieve data files from a point in the past based on one of the following methods:

• Time

• Change (sometimes called system change number [SCN])

• Log sequence number

• Restore point

The RMAN restore database until command will retrieve all data files from the most recent backup set or
image copy. RMAN will automatically determine from the until clause which backup set contains the required
data files. If you omit the until clause of the restore database command, RMAN will retrieve data files from the
latest available backup set or image copy. In some situations, that may be the behavior you desire. We recommend
you use the until clause to ensure that RMAN restores from the correct backup set or image copy. When you
issue the restore database until command, RMAN will determine how to extract the data files from any of the
following:

• Full database backup

• Incremental level 0 backup

backup as copy command
You cannot perform an incomplete database recovery on a subset of your database's online data files. When
performing incomplete database recovery, all of 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:

• Image copy backup generated by the

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 of V$DATAFILE_HEADER refers to a data file that contains one or more blocks that have an SCN
greater than or equal to the checkpoint SCN in the data file header (meaning there have been writes to the data file
since the last checkpoint). During regular database operating conditions, the FUZZY column will normally be YES .
However, after you restore a data file, if a data file has a FUZZY value of YES , you cannot open the database normally
yet; in this situation more redo needs to be applied before the database can be opened. Table 12-1 summarizes these
scenarios.