Backing Up Oracle - Computing at Cornell
Backing Up Oracle - Computing at Cornell
Backing Up Oracle - Computing at Cornell
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Chapter 8. Recovering <strong>Oracle</strong> D<strong>at</strong>abases on UNIX<br />
8.1 Restore oper<strong>at</strong>ions<br />
The earlier chapters in this UNIX section of the book have covered the<br />
various procedures and methods for backing up <strong>Oracle</strong> d<strong>at</strong>abases. Now we<br />
shall address the important topic of recovery of these d<strong>at</strong>abases.<br />
Recovering a d<strong>at</strong>abase, tablespace, or d<strong>at</strong>a file is a two-stage process. The<br />
object is first restored and then it is recovered.<br />
The restore process restores the necessary full or incremental level 0<br />
backups. Incremental backups <strong>at</strong> levels gre<strong>at</strong>er than 0 are not restored.<br />
These are restored during the subsequent recovery process.<br />
By default, the objects are restored to their original loc<strong>at</strong>ion as specified in<br />
the recovery c<strong>at</strong>alog. An altern<strong>at</strong>ive loc<strong>at</strong>ion can also be specified if required.<br />
RMAN uses the recovery c<strong>at</strong>alog to select the most current backup sets for<br />
use in the restore. The mode in which the d<strong>at</strong>abase is running determines<br />
whether a consistent or inconsistent restore oper<strong>at</strong>ion can be performed.<br />
8.1.1 Consistent d<strong>at</strong>abase recovery<br />
If the d<strong>at</strong>abase is running in NOARCHIVELOG mode, it can be restored only<br />
from a whole d<strong>at</strong>abase backup. The control files and all d<strong>at</strong>a files are restored<br />
from a consistent backup. The d<strong>at</strong>abase must be mounted but not open<br />
during the restore oper<strong>at</strong>ion.<br />
After a consistent restore, the d<strong>at</strong>abase can be opened without performing<br />
any recovery. Any upd<strong>at</strong>es to the d<strong>at</strong>abase after the backup are lost.<br />
8.1.2 Inconsistent d<strong>at</strong>abase recovery<br />
If the d<strong>at</strong>abase is running in ARCHIVELOG mode, a subset of the d<strong>at</strong>abase<br />
such as a d<strong>at</strong>a file, tablespace, or the entire d<strong>at</strong>abase can be restored to the<br />
most current st<strong>at</strong>e or to a specific point in time. This type of restore is<br />
inconsistent because the d<strong>at</strong>abase cannot be started after the restore. The<br />
restore oper<strong>at</strong>ion must be followed by a recovery oper<strong>at</strong>ion. After the<br />
recovery is finished, the d<strong>at</strong>abase can then be opened. The following objects<br />
can be restored:<br />
D<strong>at</strong>abase<br />
Tablespace<br />
D<strong>at</strong>a file<br />
© Copyright IBM Corp. 2001 107
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