Recovery Manager Restore and Recovery Techniques - Oracle 10g/11g Data and Database Management Utilities - page 148

When the incomplete recover process has finished you must take a full
database backup as soon as possible, this will be your lifeboat in case
something happens shortly after resetting the log sequence.
Test restore
A production environment cannot be conceived without a backup policy. Not having
a backup compromises overall productivity directly or indirectly related to the
database. It is pretty evident that your job and that of the people responsible for the
operation will be compromised as well. Performing a backup is a must do task in all
production environments, but testing the backup doesn't seem to be as important for
some corporations. Testing a backup is as important as performing the backup itself.
A useless backup is equivalent to not having a backup at all. At the least,
it wastes time that could have been used to formulate alternate strategies.
When asked about a backup policy most declare they have one implemented. On
the other hand, when asked about a test policy, very few hands are raised. Then,
what is the acid test for every backup? Most of the times the answer is: it is required
after a real life failure scenario. The reason why most people don't implement a test
policy is because of a lack of resources. It is very difficult for some companies to
have a duplicated environment to test the backup each time a new backup is taken.
The rman test restore feature is a convenient way to validate the backup will work as
expected when needed. The test restore rman command performs the restore cycle
without actually restoring the database
In the following scenario a retention policy of three redundant backups is defined.
A test restore is performed against each backupset.
The command issued to test each backupset is:
RESTORE VALIDATE DATABASE FROM TAG='Tag name';
If the backup is valid then it will show a validation complete message.