RMAN Fundamentals (1)

Previous versions of Oracle RDBMS, while having the capability to perform a variety of backups and restores, lacked a consistent front-end interface to perform such operations. Performing backups and restores at this point required the creation of complex scripts that ran both in Oracle and on the underlying operating system. Starting with Oracle 8.0 and 8i, a new utility called Oracle Recovery Manager (RMAN) was delivered with the RDBMS that provided a consistent front-end interface to perform most backup and restore operations. However, this interface, while greatly simplifying tasks, is still a text-based and required the DBA to learn a rather large set of command keywords. This document hopes to simplify that task.

The Recovery Catalog
RMAN prefers to store all backup information in the controlfiles of the database to be backed up (known as the TARGET) or in an optional recovery catalog. The recovery catalog is a separate oracle database that is preferably stored on separate disks and a separate node from the target. You must decide if a recovery catalog will be used or if you will only be using the target database controlfile. Oracle recommends that you always use a recovery catalog. For larger system the use of a recovery catalog can increase the backup performance. Also if the target database controlfiles are lost, recovery can become difficult if not impossible. The recovery catalog can be created in an existing database that contains other data as long as it is not the target database. In this whitepaper, we will discuss RMAN backups using a recovery catalog with SID=RCAT and the target database will have an SID of PROD.

In order to set up a database as a recovery catalog, the following steps must be performed:

1. Create a recovery catalog schema owner and grant the appropriate system privilege.

SVRMGRL> connect internal
SVRMGRL> create user rman identified by rman;
Statement processed
SVRMGRL> grant recovery_catalog_owner to rman;
Statement processed
2. Run the RMAN executable and connect to the catalog database. Once connected, create the database objects that comprise the recovery catalog. Prior to this step, but sure that tnsnames.ora, and listener.ora is properly setup for this database.
$ rman rcvcat rman/rman@RCAT
RMAN> create catalog;
Catalog created
At this point, our recovery catalog is ready for use.