Oracle Concepts - RMAN Online &
Oracle Tips by Burleson Consulting
RMAN Offline Backup
Recall that an offline backup is a backup of the
database while it is not running. Hence, to perform our backup we will shutdown
the database from RMAN and then mount the database. We will perform the backup.
Once the backup is complete we will restart the database again. Here is an
example of this process:
RMAN>sql ’alter database open’;
Once this process is complete, you have completed your
first backup. Recall that we configured a redundancy of 2 for the backups. RMAN
will reclaim the space from the flash recovery area automatically as required,
removing all unneeded backups. Later in this chapter, we will demonstrate how to
recover your database from this backup.
RMAN Online Backups
As the name implies, an online backup allows you to
backup the database while users are working. Some newer DBA’s are a little
afraid of online backups, and that somehow they might not work. We assure you
that I’ve yet to see a correctly done online backup fail to be recoverable. Most
shops these days use online backups at least for their production systems. For a
large number of shops online backups are the only backups they ever make.
In this section we will walk you through doing an online
backup. First, you will need to put your database in ARCHIVELOG mode as
discussed earlier in chapter three of this book.
Then you should configure your database and RMAN as we
describe in the above section of this book titled “Configure the Database and
RMAN for our Backup”. Once that is done, you are ready to do an online backup
Online (Hot) Backup of Oracle with RMAN
Once you setup the database and RMAN to support hot
backups, doing the backup is insanely easy. In fact, it takes fewer RMAN
commands than an offline backup does, can you believe that? Here is the RMAN
command that you will use to kick off a backup of your database:
RMAN>backup database plus
archivelog delete input;
This command will backup your database. Along with the
database backup, it will backup all the archived redo logs that have been
generated by your database (see chapter 3 for a discussion on archived redo
logs). These archived redo logs are very important to be able to recover your
database so we back them up at the same time.
You can backup archived redo logs by themselves from
time to time by issuing this command:
RMAN>backup archivelog all
Note in both examples the use of the delete input
command. This will cause the source archive redo logs to be removed once they
are backed up. Don’t worry, the delete input command will not try to delete
your database or datafiles! There are a number of other options that you may
want to explore with regards to backup retention and archived redo log
You might want to check out Robert Freeman’s other book, Oracle9i
RMAN Backup and Recovery and Oracle Database 10g RMAN Backup and Recovery for
more information on various aspects of RMAN.
Also, see my notes on the
different backup types and the
incremental cumulative and incremental differential backups.
This is an excerpt from the bestselling "Easy
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