Databases Reference
In-Depth Information
Chapter 10
Restoring the Control File
Your control file restore method is highly dependent on your backup strategy. The phrase “when you think of backups,
think of recovery” applies especially to control files. Depending on your backup methodology, the control file restore
can be effortless, or it can be complicated.
If you have enabled a fast recovery area (FRA) or are using a recovery catalog, then you'll find restoring the
control file an automated and simple process. Having RMAN do all of the heavy lifting helps ensure that you'll get this
critical file restored in a timely and accurate manner.
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We highly recommend that you enable the control file auto backup feature with the
configure controlfile autobackup on
RMAN command. This will ensure that you have a backup of your control file
after every RMAN backup and also after making database structural changes (such as adding a data file).
Note
If you're using neither a FRA nor a recovery catalog, then restoring the control file requires that you perform a few
manual steps. Manually performing steps means you must pay extra attention to the details of the task.
Control files aren't usually a source of failure. That's because they're usually multiplexed, which gives you a
high degree of protection against failure. However, these are very critical files, and you should know how to restore
them if the need arises. This chapter starts with the automated and simple methods for control file restores and then
progresses to the more complicated, manual scenarios.
Before you begin, if you have a copy of your current control file, we recommend you make a backup of it before
you issue a RMAN
restore controlfile
command. Use the
backup current controlfile
command
to back up your control file. In many scenarios, when you restore a control file it will overwrite any existing control
files.
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Anytime you restore a control file from a backup (and use it for a recovery), you are required to perform media
recovery on your entire database and then open it with the
open resetlogs
command. This is true even if you don't
restore any data files (because the control file's SCN is no longer synchronized with the SCNs in the
data files and online redo log files). You can determine whether your control file is a backup by querying the
CONTROLFILE_TYPE column of the V$DATABASE view. This chapter covers only how to restore your control file
and does not show how to restore and recover your entire database. Refer to Chapter
11
for complete recovery scenarios,
and refer to Chapter
12
for incomplete recovery situations.
Note
